930 NEW VISTAS IN HISTOPATHOLOGY LABELLED antibody molecules which can be seen under the microscope have been used in research for many years to detect and locate specific substances in sections of tissue. At this year’s summer meeting of the Pathological Society of Great Britain and Ireland a symposium on the immunoperoxidase technique revealed the remarkable potential of immunohistology in the investigation and diagnosis of tumours of lymphoreticular,12 endocrine,3 and other tissues4 and of experimental glomerulonephritis.56 Many antigens, including immunoglobulin and other plasma-proteins, viruses,8’hormones, and tumour markers,4 can be stained in conventional sections of tissues which have been processed routinely for pathological examination by fixation in formalin and embedding in paraffin wax. Thus the pathologist can relate information’ provided by antigen localisation (such as immunoglobulin deposition in the basement membrane of the renal glomeruli) to the familiar structures revealed in the same slide by haematoxylin. Two antigenic constituents can be stained simultaneously in a section, with antibodies linked to enzymes giving reaction products of different colours.9 Immunohistological staining of conventionally processed tissue sections has the advantage of applicability to specimens taken before the diagnostic indication for such staining is known; and it is useful in retrospective study of uncommon diseases. In specially prepared tissue sections, antigen can be localised at ultrastructural level.16 In some of the examples shown at the symposium, secretory products synthesised by the cell were restricted to the cisternae of the rough endoplasmic reticulum whereas antigen which was thought to have been taken up from the extracellular environment had a different distribution within the cell.10 By special fixation techniques particular antigens can be preserved and displayed--e.g., polypeptide hormones in the neuroendocrine cells of the gastrointestinal tract. 11 12 These neuroendocrine cells tend to occur singly rather than in the clusters characteristic of ordinary endocrine glands, and histological antigen localisation is contributing greatly to the study of gastrointestinal disease and the neuroendocrine system. Detection and avoidance of non-specific staining demands not only a good understanding of the immunohistochemistry of tissue antigens but also antisera whose staining properties are well defined. There is great potential value in accurately characterised monospecific antibodies produced by hybridisation of clones of neoplastic plasma-cells with single antibody-forming cells from suitably immunised animals." The fact that pre-

1. Isaacson, P., Wright, D. H. Lancet, 1978, i, 67. 2. Curran, R. C., Jones, E. L. J. Path. 1978, 125, 39. 3. Kruseman, A. C. N., Knijnenburg, G., de la Riviere, G. B., Bosman, F. T. Histopathology (in the press). 4. Heyderman, E., Neville, A. M. J. clin. Path. 1976, 30, 138. 5. Hoedemaeker, P. J., Feenstra, K., Nijkeuter, A., Arends, A. Lab. Invest.

1972,26,610. 6. Van Damme, B. J. C., Fleuren, G. J., Bakker, W. W., Vernier, R. L., Hoedemaeker, P. J. ibid. 1978, 38, 502. 7. Taylor, C. R., Mason, D. Y. Clin. exp. Immun. 1974, 18, 417. 8. Burns, J. Histochem. J. 1975, 44, 133. 9. Mason, D. Y., Sammons, R. J. clin. Path. 1978, 31, 454. 10. Poppema, S., Elema, J. D., Halie, M. R. Cancer (in the press). 11. Polak, J. M., Pearse, A. G. E., Grimelius, L., Bloom, S. R., Arimura, A. Lan-

cet, 1975, i, 1220. 12. Polak, J. M., Bloom, S. R. Invest. Cell Path. 13. Lancet, 1977, i, 1242.

(in the press).

liminary trypsinisation of formalin-fixed sections often greatly increases the intensity of immunohistological staining14 reveals that antibody molecules often do not combine with antigenic material latent in tissue sections. Such antigenic latency may lead to considerable underestimation of the amount of antigen in the tissue. Immunohistological reagents (particularly labelled antibodies) vary greatly in quality and not all laboratories use the same staining technique. Methods of standardising the results are much needed. The impact of immunohistology is being felt in many spheres and if histological antigen localisation and microscopic assay (HALMA) can be accomplished with histometry and microdensitometry, we can expect explosive advances in the understanding of normal and disordered tissue function.

MEASLES VACCINATION AFTER EXPOSURE

plasma, convalescent serum, and gammahave all been used successfully to prevent globulin2 measles in susceptible contacts but give protection for a few weeks only. In most cases, therefore, the aim has been to try to adjust the dose and timing of the gammaglobulin so that a modified attack results with consequent permanent immunity. Unfortunately this ideal is POOLED

not

easy to ensure. It is widely accepted that living vaccines given early enough in the incubation period protect, but there seems to be surprisingly little firm evidence of the value of vac-

cine alone without gamma-globulin. Watson3reported success in a small family outbreak when vaccination was carried out on the third day. The United States Public Health Service Advisory Committee on Immunisation Practices4 states that vaccination within two days of contact will usually protect. Short-lived measles-like symptoms (fever, cough, and rash) are common reactions to the vaccine which make the evaluation of protection in contacts more difficult. Ruuskanen and his colleaguess report a study designed to overcome this difficulty. They compared reactions to the attenuated Schwartz strain in 442 normal children and in 74 children vaccinated 1-14 days after exposure. The exact exposure date could not be estimated. There were no significant differences in severity between the two groups but there was an unusually rapid onset of fever (2-4 days) in 10 exposed children which Ruuskanen et al. attributed to a prolonged incubation period. Clinical measles developed in only 5 of the exposed children. This suggests that measles vaccination without gamma-globulin is a safe and effective means of ending an epidemic and that protection may well be achieved by vaccination later in the incubation period than the third day. What is now needed is a controlled trial in susceptible contacts at different times after exposure. This should not be difficult to organise in families or small residential groups. With the high infectivity of measles there would be no need for large numbers. 14. Huang, S. N., Minassian, H., More, J. D. Lab. Invest. 1976, 35, 383. 1. McKendrick, G. D. W., Seville, R. H. Br. med. J. 1946, ii, 899. 2. Greenberg, M., Frank, S., Rutstein, D. D.J. Am. med. Ass. 1944, 126, 944. 3. Watson, G. I. Br. med. J. 1963, i, 860. 4. Morbid. Mortal wkly Rep. 1976, 25, 359. 5. Ruuskanen, O., Salmi, T. T., Halonen, P.J. Pediat. 1978, 93, 43.

New vistas in histopathology.

930 NEW VISTAS IN HISTOPATHOLOGY LABELLED antibody molecules which can be seen under the microscope have been used in research for many years to detec...
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