578
of them in a poor light. One of the most has been the technique devised by popular GRAVLEE. Irrigation of the uterine cavity with a negative pressure jet-washer produces either gross tissue fragments suitable for histological assessment or cytological material which can be directly smeared or subjected to further filtration processes. CASEY14 reports that, without anaesthesia, the device is easily inserted into the cervix of about one in two symptomless women over 40. In about a quarter of the patients insertion was somewhat difficult, while in the remainder it was very difficult or impossible. A quarter of the patients show
some
reported moderate to severe discomfort during the procedure. In this study 98% of irrigation samples were suitable for histological and cytological interpretation. But although these favourable results have been reproduced by some workers, IS 16 there is increasing disillusionment with the Gravlee technique. ALFONS017 reviewed the data on 221 women in eight studies between 1970 and 1975 and found a 43% false-negative rate in the detection of endometrial adenomatous hyperplasia. The results for endometrial carcinoma were better, but again the washings were positive in only 233 (80%) of 289 18 women seen by twelve groups. TWIGGS and his co-workers in California employed uterine irrigation in 556 abnormal uterine or postmenopausal bleeders who presented as outpatients. Only 2 of 16 women with adenomatous hyperplasia had the diagnosis confirmed by washings while, out of 25 with adenocarcinoma proven at later curethad negative and 10 had unsatisfactory 4 tage, women
Such high false-positive and false-negative rates forced them to conclude that "in the clinical setting outside of the controlled environment of a formal study" this method was unreliable. What other screening techniques exist besides outright dilatation and curettage under general anaesthesia ? One possibility is outpatient curettage, either with the steel aspiration curette (Vabra) or with a small conventional curette. Steel aspiration curettage is not very uncomfortable (only 2 out of 50 women in one study19 described the pain as severe); satisfactory endometrial specimens are obtained and the accuracy seems to be far better than that of the uterine irrigation technique. 19 11 Passage of the 3 mm diameter metal cannula into the postmenopausal cervix seems to be
washings.
Casey, M. J., Madden, T. J. in Consensus on Menopause Research (edited by P. A. Van Keep, R. B. Greenblatt, and M. Albeaux-Fernet); p. 139. Lancaster, 1976. 15. Henderson, S. R., Roxburgh, D. R., Bobrow, L. G., Pollard, S. M., Greening, S. E. Br. J. Obstet. Gynœc. 1975, 82, 976. 16. Bibbo, M., Rice, A. M., Wied, G. Obstet. Gynec. 1974, 43, 253. 17. Alfonso, J. F. ibid. 1975, 46, 141. 18. Twiggs, L. B., Di Saia, P. J., Morrow, C. P., Townsend, D. E., Schwinn, C. E. J. Am. med. Ass. 1976, 235, 2748. 19. Cohen, C. J., Gusberg, S. B., Koffler, D. Gynec. Oncol. 1974, 2, 279. 20. Denis, R., Barnett, J. M., Forbes, S. E. Obstet. Gynec. 1973, 42, 672. 14.
easier than passage of the 4.5 mm tip of the irrigation device. Other methods for obtaining endometrial specimens have made use of swabs, sponges, and brushes; all seem to increase intrauterine pressure (with the theoretical risk of extrauterine contamination), are disliked by patients, and do not seem to obtain uniform endometrial samples. How then should the woman on hormone replacement therapy be screened? Since oestrogens probably stimulate the endometrium in doserelated fashion,11 periodic sampling of the endometrium seems essential: a year might be an acceptable interval between tests, but it should be less if irregular bleeding occurs. The Chelsea Hospital Group, who have undertaken one of the first prospective studies on the effect of exogenous oestrogens on the postmenopausal endometrium, suggest sampling at six-monthly intervals. Aspiration curettage would probably be sufficient for these tests. But is all this monitoring being too cautious? The incidence rate of endometrial carinoma in the U.S.A. seems not to have risen between the last two major national cancer surveys of 1948-49 and 1969-71,21 and indeed mortality in this time has fallen from 9.1 to 4/100 000. In the U.K. there has been no increase in mortality from endometrial cancer up to 1973 or in incidence up to 1970;22 the percentage of postmenopausal women who have been on oestrogen replacement is small, probably about 6% of those between 50 and 59.22 Existing data make a case for some form of surveillance, and this could be arranged in National Health Service clinics now providing hormone replacement. Maybe the economists would argue for screening only women at high risk of endometrial cancer. GUSBERG10 has re-emphasised the tendency of the diabetic, the obese, and the nullipara to get this disease. Giving a progestagen in sequential form might also be cost-effective, but the analysis will be difficult since uterine cancer is seldom fatal.
Reactivation of Hepatitis-B Virus WHATEVER their ancestral origins,1 viruses must have been exposed to intense evolutionary presfrom a hostile external environment which includes the internal environment of animal hosts which, during their own evolution, acquired ever more elaborate defence-mechanisms. The enormous variation in the patterns of host/virus interactions and the wide spectrum of clinical illness which results are perhaps visible reflections of these sures
21. 22. 1.
Cramer, D. W., Cutler, S. J., Christine, B. Gynec. Oncol. 1974, 2, 130. Doll, R., Kinlen, L. J., Skegg, D. C. G. Br. med. J. 1976, i, 1071. Almeida, J. D. Br. J. Hosp. Med. 1973, 10, 368.
579
evolutionary pressures. The most successful parasite is, of course, the one which does not provoke any host reaction. Some viruses
are
able
to
achieve
this and the resultant carrier state is not necessarily detrimental to the host. A good example is the hepatitis-B virus, for there must be millions of entirely healthy HBsAg-positive individuals throughout the world with no evidence of any structural damage to the liver. The mechanism here seems to be a specific immunological unresponsiveness to the hepatitis-B surface antigen2which is perhaps genetically determined.3Several viruses survive in their original host despite immune recognition by considerably reducing the rate of production of new virus particles. Infected cells are not eliminated and such latent infection may be reactivated when the internal host environment changes. Recurrent coldsores due to reactivation of the herpes-simplex virus are perhaps the most painfully obvious example of such behaviour. On p. 558 Dr NAGINGTON and his co-workers present more subtle immunological evidence suggesting that reactivation may be part of the repertoire of the hepatitis-B virus. They have examined 380 first sera from patients admitted to the Cambridge transplantation unit for the presence of HBsAg and for antibody to the surface and core antigens. The crux of their case is that there were 6 patients whose initial sera contained antibody to the hepatitis B core antigen (HBcAg) but not to the surface antigen (HBsAg) and of these 3 became HBsAg-positive after transplantation. In contrast, antigenaemia occurred in none of the 17 whose initial sera contained antibodies to both antigens and in only 3 (0.8%) of the remaining 357 patients without anti-HBc. The most obvious explanation for these highly significant differences is that the anti-HBc was a marker of previous infection in these patients and that reactivation occurred after transplantation. But the alternative explanationreinfection-must first be excluded. Reports of the coexistence of antibody and antigen of different subtypes in the same serum4-6 show clearly that a second infection can occur in previously exposed individuals, and immunosuppressive therapy would doubtless facilitate reinfection by decreasing any protective immunity. However, it seems most unlikely that the group with anti-HBc in the first serum sample would be more susceptible to a second infection. A remote possibility is that it was really the absence of anti-HBs that was the important factor rather than the presence of anti-HBc, 2 Lee, W. M., Reed, W. D., Mitchell, C. G., Woolf, I. L., Dymock, I. W., Eddleston, A. L. W. F., Williams, R. Gut, 1975, 16, 416. 3. Blumberg, B. S., London, W. T., Sutnick, A. I. Am. J. clin. Path. 1971, 56, 265.
4. Sasaki, T., Ohkubo, J., Yamashita, Y., Imai, M., Miyakawa, Y., Mayumi, M.J. Immun. 1976, 117, 2258. 5. Koziol, D. E., Alter, H. J., Kirchner, J. P., Holland, P. V. ibid. p. 2260. 6. Le Bouvier, G. L.,
J. ibid. p. 2262.
Capper,
R. A.,
Williams, A. E., Pelletier, M., Katz, A.
and here the results of radioimmunoassay for anti-HBs in those without anti-HBc will be of great
interest. Evidence supporting the concept of latent hepatitis-B virus infection comes from the studies of
HOOFNAGLE, GERETY, and BARKER’ who suggested than three years ago that there may be some individuals whose serum is negative for HBsAg by radioimmunoassay but who are carriers of the hepatitis-B virus. They came to this conclusion after surveying 200 volunteer blood-donors for anti-HBc. Serum from 1 individual was positive for anti-HBc but negative for HBsAg and anti-HBs, and over a 7 month follow-up the findings remained constant.8 In subjects with both anti-HBs and anti-HBc, re-exposure to known HBsAg-positive blood was associated with an immediate increase in anti-HBs titre but no change in anti-HBc levels.’ From this, HOOFNAGLE et al. argued that persistence of anti-HBc in the absence of anti-HBs was unlikely to be due to repeated exposure to HBsAg and might instead be a reflection of continued viral replication, but at such a reduced rate that the virus produced could not be detected even by the most sensitive immunological techniques. In theory, such serum could be infectious, and by testing 16 blood-donors who were implicated in cases of post-transfusion hepatitis, they identified a further 3 individuals whose sera were positive for anti-HBc alone.8 However, the type of post-transfusion hepatitis in the recipients of blood from the donors was not known and proof of infectivity for hepatitis-B virus infection would require prospective evaluation of patients transfused with HBsAgnegative, anti-HBc positive blood, or infectivity studies in susceptible animals. Some of the factors involved in the induction of latency have been identified. In the case of herpessimplex virus infection, the presence of IgG antibodies to viral antigens is essential,9 and, after passive transfer of anti-viral antibody, herpes-simplex virus D.N.A. synthesis is much reduced.9 JOSEPH and OLDSTONE, working with measles-virus infected hela cells, showed that after 12 hours exposure of these cells to antibodies to measles virus, surface viral antigenic expression was greatly diminished 10 and at this time neither antibody and complement,10 nor sensitised peripheral lymphocytes" were able to kill infected target cells. In addition, there were none of the usual cytopathic effects of the virus, although the treated cells continued to express measles-virus antigens in their cytoplasm. 10 There are obvious similarities between this in-vitro model and the clinical situation in more
7. 8.
Hoofnagle, J. H., Gerety, R. J., Barker, L. F. Lancet, 1973, ii, 869. Hoofnagle, J. H., Gerety, R. J., Ni, L. Y., Barker, L. F. New Engl. J. Med.
9. 10. 11.
1974, 290, 1336. Stevens, J., Cook, M.J.Immun. 1974, 113, 1685. Joseph, B. S., Oldstone, M. B. A. J. exp. Med. 1975, 142, 864. Oldstone, M. B. A. in Advanced Medicine (edited by D. K. Peters); p. 32. Bath, 1976.
580
where measles antibody is present in high titre.12 Measles-virus nucleocapsids can be found in the cytoplasm and nuclei of cells from brain-biopsy specimens but the surfaces of these cells show little or no viral antigen.13 In one report of the distribution of HBsAg in liver-biopsy material, there were 3 patients in whom HBsAg was detected in the cytoplasm of some hepatocytes but serum was negative for HBsAg by radioimmunoassay.14 The results of tests for anti-HBc in these cases would obviously be of considerable interest. The mechanisms involved in reactivation are even more obscure than those responsible for the induction of latency. Transplantation is clearly a potent stimulus. One group reported evidence of active cytomegalovirus infection in 25 of 26 patients during the first 7 months after kidney transplantation and reactivation of herpes simplex and varicella-zoster in 35% and 24%, respectively.15 In view of the evidence linking antibody with the induction of latency, the immunosuppressive treatment associated with transplantation seems the obvious trigger for reactivation. However, there is some evidence that immunosuppressive therapy is insufficient on its own 16 and that the immune stimulation provided by the allograft may be a very important additional factor. 17 Even the two factors in combination rarely induce reactivation of the hepatitis-B virus-perhaps because of the protective effect of the continued presence of anti-HBs in most of the cases. However, these results emphasise the importance of continued surveillance in renal units to ensure early isolation of any patient who becomes HBsAg positive, whether through reactivation or primary infection.
subacute
-
sclerosing panencephalitis
have predominantly non-precipitating antibodies the antigen.2 The antibody may be non-precipitating because it binds weakly to antigen (i.e., it is of low affinity). Such antibody is poor at antigen elimination3 and the inbred strains of mice, which are prone to contract nephritis when infected to to
neonatally with lymphocytic choriomeningitis virus, produce low-affinity antibody.4 It is therefore possible that individuals who acquire persistent damaging soluble immune complexes after antigen contact, do so because of an underlying immunodeficiency. Not all immune complexes are damaging, since sensitive methods of detection show low levels in people with no apparent disease. Immune complexes vary in size, antibody class, and complement-binding capacity as well as antigen. Such variation probably occurs within and between disease groups. If we could identify the constituents of complexes we might devise more rational treatment for these diseases. None of the many published methods of immune-complex detection is entirely satisfactory for such analysis,5 and not all methods detect the same complexes. Most of the techniques depend on physicochemical properties of complexes (cryoprecipitation or polyethylene-glycol precipitation), on recognition-proteins such as human Clq or rheumatoid factor, or on cells which detect complexes by C36 or Fc receptors.s Several of the tests require heat inactivation of complement before analysis of sera, and this probably gives erroneous resultsfalse positives due to heat aggregation of IgG, and false negatives due to heat destruction of complexes. Also, those tests which employ Clq as a recognition-protein for immune complexes are prone to false positives due to reaction of Clq with free D.N.A., bacterial endotoxin, and other serum proteins.6But despite the deficiencies of existing
Disease
techniques, immune-complex measurement can already be useful. BAYER and colleagues found immune complexes in the sera of patients with infec-
soluble antigen/antibody complexes probably contribute to many diseases, from the acute infectious to the chronic allergic. The evidence that immune complexes can be damaging comes largely from the acute and chronic nephritis in animals which results from immune-complex deposition after single or repeated doses of antigen.Few animals acquire chronic nephritis even with repeated dosage, but these animals prove
tive endocarditis due to various bacteria and moulds. The Raji-cell radioimmunoassay,* which detects complexes containing IgG by means of a C3b receptor, gave significantly higher values in the patients with extravalvular manifestations than in those without. Arthritis, splenomegaly, nephritis, and thrombocytopenia in such cases may well arise from circulating soluble immune complexes. The observation that levels of complexes correlated with
12.
2. Pincus, T., Haberkern, R., Christian, C. L. J. exp. Med. 1968, 127, 819. 3. Alpers, J. H., Steward, M. W., Soothill, J. F. Clin. exp. Immun. 1972, 12, 121. 4. Soothill, J. F., Steward, M. W. ibid. 1971, 9, 193. 5. Ann. rheum. Dis. 1977, 36, suppl. 1 (edited by R. N. Maini and E. J.
Immune
Complexes in Health and
CIRCULATING
Connolly, J. H., Allen,
I.
V., Hurwitz, L. J., Millar, J. H. D. Lancet, 1967,
i, 542. 13.
Lampert, P. W., Joseph, B. S., Oldstone, M. B. A. in Progress in Neuropathology, vol. III (edited by H. M. Zimmerman). New York, 1975. 14. Ray, M. B., Desmet, V. J., Bradburne, A. F., Desmyter, J., Feveny, J., De Groote, J. Gastroenterology, 1976, 71, 462. 15. Fiala, M., Payne, J. E., Borne, T. V., Moore, T. C., Heale, W., Montgomerie, J. Z., Chatterjee, S. N., Guze, L. B. J. inf. Dis. 1975, 132, 421. 16. Hill, T. J., Blyth, W. A. Lancet, 1976, i, 397. 17. Hirsch, M. S., Ellis, D. A., Black, P. H., Monaco, A. P., Wood, M. L. Science, 1973, 180, 500. 1. Cochrane, C. G., Koffler, D. Adv. Immun. 1973, 16, 185.
Holborow). 6. Sobel, A. T., Bokisch, V. A., Muller-Eberhard, H. J. J. exp. Med. 1975, 142, 139. 7. Bayer, A. S., Theofilopoulous, A. N., Eisenberg, R., Dixon, F. J., Guze, L. B. New Engl. J. Med. 1976, 295, 1500. 8. Theofilopoulos, A. N., Wilson, C. B., Dixon, F. J. J. clin. Invest. 1976, 57, 169.
of them in a poor light. One of the most has been the technique devised by popular GRAVLEE. Irrigation of the uterine cavity with a negative pressure jet-washer produces either gross tissue fragments suitable for histological assessment or cytological material which can be directly smeared or subjected to further filtration processes. CASEY14 reports that, without anaesthesia, the device is easily inserted into the cervix of about one in two symptomless women over 40. In about a quarter of the patients insertion was somewhat difficult, while in the remainder it was very difficult or impossible. A quarter of the patients show
some
reported moderate to severe discomfort during the procedure. In this study 98% of irrigation samples were suitable for histological and cytological interpretation. But although these favourable results have been reproduced by some workers, IS 16 there is increasing disillusionment with the Gravlee technique. ALFONS017 reviewed the data on 221 women in eight studies between 1970 and 1975 and found a 43% false-negative rate in the detection of endometrial adenomatous hyperplasia. The results for endometrial carcinoma were better, but again the washings were positive in only 233 (80%) of 289 18 women seen by twelve groups. TWIGGS and his co-workers in California employed uterine irrigation in 556 abnormal uterine or postmenopausal bleeders who presented as outpatients. Only 2 of 16 women with adenomatous hyperplasia had the diagnosis confirmed by washings while, out of 25 with adenocarcinoma proven at later curethad negative and 10 had unsatisfactory 4 tage, women
Such high false-positive and false-negative rates forced them to conclude that "in the clinical setting outside of the controlled environment of a formal study" this method was unreliable. What other screening techniques exist besides outright dilatation and curettage under general anaesthesia ? One possibility is outpatient curettage, either with the steel aspiration curette (Vabra) or with a small conventional curette. Steel aspiration curettage is not very uncomfortable (only 2 out of 50 women in one study19 described the pain as severe); satisfactory endometrial specimens are obtained and the accuracy seems to be far better than that of the uterine irrigation technique. 19 11 Passage of the 3 mm diameter metal cannula into the postmenopausal cervix seems to be
washings.
Casey, M. J., Madden, T. J. in Consensus on Menopause Research (edited by P. A. Van Keep, R. B. Greenblatt, and M. Albeaux-Fernet); p. 139. Lancaster, 1976. 15. Henderson, S. R., Roxburgh, D. R., Bobrow, L. G., Pollard, S. M., Greening, S. E. Br. J. Obstet. Gynœc. 1975, 82, 976. 16. Bibbo, M., Rice, A. M., Wied, G. Obstet. Gynec. 1974, 43, 253. 17. Alfonso, J. F. ibid. 1975, 46, 141. 18. Twiggs, L. B., Di Saia, P. J., Morrow, C. P., Townsend, D. E., Schwinn, C. E. J. Am. med. Ass. 1976, 235, 2748. 19. Cohen, C. J., Gusberg, S. B., Koffler, D. Gynec. Oncol. 1974, 2, 279. 20. Denis, R., Barnett, J. M., Forbes, S. E. Obstet. Gynec. 1973, 42, 672. 14.
easier than passage of the 4.5 mm tip of the irrigation device. Other methods for obtaining endometrial specimens have made use of swabs, sponges, and brushes; all seem to increase intrauterine pressure (with the theoretical risk of extrauterine contamination), are disliked by patients, and do not seem to obtain uniform endometrial samples. How then should the woman on hormone replacement therapy be screened? Since oestrogens probably stimulate the endometrium in doserelated fashion,11 periodic sampling of the endometrium seems essential: a year might be an acceptable interval between tests, but it should be less if irregular bleeding occurs. The Chelsea Hospital Group, who have undertaken one of the first prospective studies on the effect of exogenous oestrogens on the postmenopausal endometrium, suggest sampling at six-monthly intervals. Aspiration curettage would probably be sufficient for these tests. But is all this monitoring being too cautious? The incidence rate of endometrial carinoma in the U.S.A. seems not to have risen between the last two major national cancer surveys of 1948-49 and 1969-71,21 and indeed mortality in this time has fallen from 9.1 to 4/100 000. In the U.K. there has been no increase in mortality from endometrial cancer up to 1973 or in incidence up to 1970;22 the percentage of postmenopausal women who have been on oestrogen replacement is small, probably about 6% of those between 50 and 59.22 Existing data make a case for some form of surveillance, and this could be arranged in National Health Service clinics now providing hormone replacement. Maybe the economists would argue for screening only women at high risk of endometrial cancer. GUSBERG10 has re-emphasised the tendency of the diabetic, the obese, and the nullipara to get this disease. Giving a progestagen in sequential form might also be cost-effective, but the analysis will be difficult since uterine cancer is seldom fatal.
Reactivation of Hepatitis-B Virus WHATEVER their ancestral origins,1 viruses must have been exposed to intense evolutionary presfrom a hostile external environment which includes the internal environment of animal hosts which, during their own evolution, acquired ever more elaborate defence-mechanisms. The enormous variation in the patterns of host/virus interactions and the wide spectrum of clinical illness which results are perhaps visible reflections of these sures
21. 22. 1.
Cramer, D. W., Cutler, S. J., Christine, B. Gynec. Oncol. 1974, 2, 130. Doll, R., Kinlen, L. J., Skegg, D. C. G. Br. med. J. 1976, i, 1071. Almeida, J. D. Br. J. Hosp. Med. 1973, 10, 368.
579
evolutionary pressures. The most successful parasite is, of course, the one which does not provoke any host reaction. Some viruses
are
able
to
achieve
this and the resultant carrier state is not necessarily detrimental to the host. A good example is the hepatitis-B virus, for there must be millions of entirely healthy HBsAg-positive individuals throughout the world with no evidence of any structural damage to the liver. The mechanism here seems to be a specific immunological unresponsiveness to the hepatitis-B surface antigen2which is perhaps genetically determined.3Several viruses survive in their original host despite immune recognition by considerably reducing the rate of production of new virus particles. Infected cells are not eliminated and such latent infection may be reactivated when the internal host environment changes. Recurrent coldsores due to reactivation of the herpes-simplex virus are perhaps the most painfully obvious example of such behaviour. On p. 558 Dr NAGINGTON and his co-workers present more subtle immunological evidence suggesting that reactivation may be part of the repertoire of the hepatitis-B virus. They have examined 380 first sera from patients admitted to the Cambridge transplantation unit for the presence of HBsAg and for antibody to the surface and core antigens. The crux of their case is that there were 6 patients whose initial sera contained antibody to the hepatitis B core antigen (HBcAg) but not to the surface antigen (HBsAg) and of these 3 became HBsAg-positive after transplantation. In contrast, antigenaemia occurred in none of the 17 whose initial sera contained antibodies to both antigens and in only 3 (0.8%) of the remaining 357 patients without anti-HBc. The most obvious explanation for these highly significant differences is that the anti-HBc was a marker of previous infection in these patients and that reactivation occurred after transplantation. But the alternative explanationreinfection-must first be excluded. Reports of the coexistence of antibody and antigen of different subtypes in the same serum4-6 show clearly that a second infection can occur in previously exposed individuals, and immunosuppressive therapy would doubtless facilitate reinfection by decreasing any protective immunity. However, it seems most unlikely that the group with anti-HBc in the first serum sample would be more susceptible to a second infection. A remote possibility is that it was really the absence of anti-HBs that was the important factor rather than the presence of anti-HBc, 2 Lee, W. M., Reed, W. D., Mitchell, C. G., Woolf, I. L., Dymock, I. W., Eddleston, A. L. W. F., Williams, R. Gut, 1975, 16, 416. 3. Blumberg, B. S., London, W. T., Sutnick, A. I. Am. J. clin. Path. 1971, 56, 265.
4. Sasaki, T., Ohkubo, J., Yamashita, Y., Imai, M., Miyakawa, Y., Mayumi, M.J. Immun. 1976, 117, 2258. 5. Koziol, D. E., Alter, H. J., Kirchner, J. P., Holland, P. V. ibid. p. 2260. 6. Le Bouvier, G. L.,
J. ibid. p. 2262.
Capper,
R. A.,
Williams, A. E., Pelletier, M., Katz, A.
and here the results of radioimmunoassay for anti-HBs in those without anti-HBc will be of great
interest. Evidence supporting the concept of latent hepatitis-B virus infection comes from the studies of
HOOFNAGLE, GERETY, and BARKER’ who suggested than three years ago that there may be some individuals whose serum is negative for HBsAg by radioimmunoassay but who are carriers of the hepatitis-B virus. They came to this conclusion after surveying 200 volunteer blood-donors for anti-HBc. Serum from 1 individual was positive for anti-HBc but negative for HBsAg and anti-HBs, and over a 7 month follow-up the findings remained constant.8 In subjects with both anti-HBs and anti-HBc, re-exposure to known HBsAg-positive blood was associated with an immediate increase in anti-HBs titre but no change in anti-HBc levels.’ From this, HOOFNAGLE et al. argued that persistence of anti-HBc in the absence of anti-HBs was unlikely to be due to repeated exposure to HBsAg and might instead be a reflection of continued viral replication, but at such a reduced rate that the virus produced could not be detected even by the most sensitive immunological techniques. In theory, such serum could be infectious, and by testing 16 blood-donors who were implicated in cases of post-transfusion hepatitis, they identified a further 3 individuals whose sera were positive for anti-HBc alone.8 However, the type of post-transfusion hepatitis in the recipients of blood from the donors was not known and proof of infectivity for hepatitis-B virus infection would require prospective evaluation of patients transfused with HBsAgnegative, anti-HBc positive blood, or infectivity studies in susceptible animals. Some of the factors involved in the induction of latency have been identified. In the case of herpessimplex virus infection, the presence of IgG antibodies to viral antigens is essential,9 and, after passive transfer of anti-viral antibody, herpes-simplex virus D.N.A. synthesis is much reduced.9 JOSEPH and OLDSTONE, working with measles-virus infected hela cells, showed that after 12 hours exposure of these cells to antibodies to measles virus, surface viral antigenic expression was greatly diminished 10 and at this time neither antibody and complement,10 nor sensitised peripheral lymphocytes" were able to kill infected target cells. In addition, there were none of the usual cytopathic effects of the virus, although the treated cells continued to express measles-virus antigens in their cytoplasm. 10 There are obvious similarities between this in-vitro model and the clinical situation in more
7. 8.
Hoofnagle, J. H., Gerety, R. J., Barker, L. F. Lancet, 1973, ii, 869. Hoofnagle, J. H., Gerety, R. J., Ni, L. Y., Barker, L. F. New Engl. J. Med.
9. 10. 11.
1974, 290, 1336. Stevens, J., Cook, M.J.Immun. 1974, 113, 1685. Joseph, B. S., Oldstone, M. B. A. J. exp. Med. 1975, 142, 864. Oldstone, M. B. A. in Advanced Medicine (edited by D. K. Peters); p. 32. Bath, 1976.
580
where measles antibody is present in high titre.12 Measles-virus nucleocapsids can be found in the cytoplasm and nuclei of cells from brain-biopsy specimens but the surfaces of these cells show little or no viral antigen.13 In one report of the distribution of HBsAg in liver-biopsy material, there were 3 patients in whom HBsAg was detected in the cytoplasm of some hepatocytes but serum was negative for HBsAg by radioimmunoassay.14 The results of tests for anti-HBc in these cases would obviously be of considerable interest. The mechanisms involved in reactivation are even more obscure than those responsible for the induction of latency. Transplantation is clearly a potent stimulus. One group reported evidence of active cytomegalovirus infection in 25 of 26 patients during the first 7 months after kidney transplantation and reactivation of herpes simplex and varicella-zoster in 35% and 24%, respectively.15 In view of the evidence linking antibody with the induction of latency, the immunosuppressive treatment associated with transplantation seems the obvious trigger for reactivation. However, there is some evidence that immunosuppressive therapy is insufficient on its own 16 and that the immune stimulation provided by the allograft may be a very important additional factor. 17 Even the two factors in combination rarely induce reactivation of the hepatitis-B virus-perhaps because of the protective effect of the continued presence of anti-HBs in most of the cases. However, these results emphasise the importance of continued surveillance in renal units to ensure early isolation of any patient who becomes HBsAg positive, whether through reactivation or primary infection.
subacute
-
sclerosing panencephalitis
have predominantly non-precipitating antibodies the antigen.2 The antibody may be non-precipitating because it binds weakly to antigen (i.e., it is of low affinity). Such antibody is poor at antigen elimination3 and the inbred strains of mice, which are prone to contract nephritis when infected to to
neonatally with lymphocytic choriomeningitis virus, produce low-affinity antibody.4 It is therefore possible that individuals who acquire persistent damaging soluble immune complexes after antigen contact, do so because of an underlying immunodeficiency. Not all immune complexes are damaging, since sensitive methods of detection show low levels in people with no apparent disease. Immune complexes vary in size, antibody class, and complement-binding capacity as well as antigen. Such variation probably occurs within and between disease groups. If we could identify the constituents of complexes we might devise more rational treatment for these diseases. None of the many published methods of immune-complex detection is entirely satisfactory for such analysis,5 and not all methods detect the same complexes. Most of the techniques depend on physicochemical properties of complexes (cryoprecipitation or polyethylene-glycol precipitation), on recognition-proteins such as human Clq or rheumatoid factor, or on cells which detect complexes by C36 or Fc receptors.s Several of the tests require heat inactivation of complement before analysis of sera, and this probably gives erroneous resultsfalse positives due to heat aggregation of IgG, and false negatives due to heat destruction of complexes. Also, those tests which employ Clq as a recognition-protein for immune complexes are prone to false positives due to reaction of Clq with free D.N.A., bacterial endotoxin, and other serum proteins.6But despite the deficiencies of existing
Disease
techniques, immune-complex measurement can already be useful. BAYER and colleagues found immune complexes in the sera of patients with infec-
soluble antigen/antibody complexes probably contribute to many diseases, from the acute infectious to the chronic allergic. The evidence that immune complexes can be damaging comes largely from the acute and chronic nephritis in animals which results from immune-complex deposition after single or repeated doses of antigen.Few animals acquire chronic nephritis even with repeated dosage, but these animals prove
tive endocarditis due to various bacteria and moulds. The Raji-cell radioimmunoassay,* which detects complexes containing IgG by means of a C3b receptor, gave significantly higher values in the patients with extravalvular manifestations than in those without. Arthritis, splenomegaly, nephritis, and thrombocytopenia in such cases may well arise from circulating soluble immune complexes. The observation that levels of complexes correlated with
12.
2. Pincus, T., Haberkern, R., Christian, C. L. J. exp. Med. 1968, 127, 819. 3. Alpers, J. H., Steward, M. W., Soothill, J. F. Clin. exp. Immun. 1972, 12, 121. 4. Soothill, J. F., Steward, M. W. ibid. 1971, 9, 193. 5. Ann. rheum. Dis. 1977, 36, suppl. 1 (edited by R. N. Maini and E. J.
Immune
Complexes in Health and
CIRCULATING
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