Volume 69 November 1976

7

873

Section of Endocrinology President Professor Reginald Hall

Meeting 24 March 1976

Short Papers Autoimmune Thyroiditis in T-cell-depleted Rats by W J Irvine FRCPEd (Department ofClinical Immunologyl Endocrinology, Royal Infirmary, Edinburgh, EH3 9 YW, and University Immunology Laboratories, Forrest Road, Edinburgh) A working hypothesis with regard to the pathogenesis of autoimmune disease in man is that there is a deficiency in the control mechanisms within the immune system that allows autoimmune reactions to develop unimpeded. It is suggested that this deficiency is in relation to the suppressor T-cells (a subpopulation of thymus-dependent lymphocytes) which normally have an important role in holding back the development of autoimmune reactions be they humoral or cellular. In (a)

NORMAL STATE

the absence of the appropriate suppressor T-cells, autoantibodies may be made to B-dependent antigens or (in the presence of helper T-lymphocytes) also to T-dependent antigens, such as thyroglobulin (Fig 1). This hypothesis has been put forward by Allison et al. (1971), Penhale et al. (1973) and Irvine (1974). To test this hypothesis rats were deliberately partially depleted of T-lymphocytes by neonatal thymectomy followed by sublethal irradiation (Fig 2). Such animals are referred to as Tx-X rats. Such treatment lowers the peripheral blood lymphocyte count, depresses the transformation of peripheral blood lymphocytes in response to PHA stimulation and depletes the T-celldependent areas in the lymph nodes and spleen (Fig 3). Depending on the strain of inbred rat used, such treatment is followed by the development in a high percentage of the animals of chronic thyroiditis associated with antibodies to (b)

Autowntigen

Suppressor

Inhibition

T cell

Heelper T cell

AUTOIMMUNE STATE (after Tx-X) Autoantigen

Suppressor.., T cell absent

T

No autoantibody * INHIBITION OF AUTOREACTIVE B CELL

*Heper T cell

Autoontibody TRIGGERING OF AUTOREACTIVE B CELL

Fig 1 A hypothesis for the etiology of autoimmunity. Tx-X, neonatal thvmectomny followed by sublethal irradiation inducing a partial depletion of T-lympihocytes. (Reproducedfrom Penhale, Farmer & Irvine 1975 by kindpermission)

874 Proc. roy. Soc. Med. Volume 69 November 1976 Histology,

serology,

Kill

etc.

Fig 2 Thymectomy and irradiation schedule used in P VG/c rats for the induction of autoimmune thyroiditis. Tx, thymectomy. X, irradiation. (Reproducedfrom Penhale, Farmer & Irvine 1975 by kindpermission)

200 rod

0

Tx

x

3

5

x

x

x

10 Time after birth (weeks)

15

19

SEVERITY OF THYROIDrTIS AND TITRE OF AUTOANTIBODY I RAT STRAINS (Me + SEM)

IMMUNOLOGICAL STATUS OF Tx-X RATS

CAM

Peripheral blood lymphocytes count PHA transformation

~

~

~

PG/

AG

L

0 s$1

Lymph node cells S.

T cells A

Spleen cells T cells

Fig 3 Evidence for T-cell depletion induced by the schedule shown in Fig 2

thyroglobulin in the serum even when the thyroid was protected from irradiation by a lead collar (Penhale et al. 1973). Among the most susceptible of strains is PVG/c, while among the least susceptible is CAM (Fig 4). No evidence could be found for an association between susceptibility to this form of thyroiditis and histocompatibility types, although this point was not extensively investigated. This is in contrast to thyroiditis induced by immunization with thyroglobulin in Freund's adjuvant in rats (Penhale, Farmer, Urbaniak & Irvine 1975). The model is similar to autoimmune chronic thyroiditis in man in so far that once the thyroiditis has been induced it is persistent and not transitory as tends to be the case with the classical form of autoimmune thyroiditis induced by immunizaTable I Effect of sex on the susceptibility of PVG/c strain rats to thyroiditis after Tx-X Females 30

Total No.

Males 28

Pathology: Mean ± s.e. Incidence

1.5 - 0.3 2.7 ± 0.3 82.5 39.2

Autoantibody: 3.9+0.7 6.0+0.8 Mean s.e. 79.2 39.2 Incidence

Fig 4 The influence ofgenetics on the susceptibility of rats to develop autoimmune thyroiditisfollowing T-cell depletion PVG/c, WAG, LH, CAM, different inbred strains of rat. The standard error of the means of the thyroiditis score and of the log2 thyroglobtulin antibody titres are shown. For thyroiditis scoring see Penhale et al. (1973)

tion with thyroid antigen emulsified in complete Freund's adjuvant. The thyroiditis that develops in T-cell-depleted rats is associated with goitre, and female rats develop the lesion more frequently than do males (Table 1). In man, Hashimoto thyroiditis has not yet been shown to be linked with any particular histocompatibility type, in contrast to thyrotoxicosis. It was argued that, if the induction of thyroid autoimmunity by this means in a susceptible strain of rat is indeed due to a relative depletion of suppressor T-lymphocytes, it should be possible to reconstitute the animals with suppressor T-lymphocytes from normal rats of the same inbred strain (syngeneic) so that normal control within the immune system is restored. Reconstitution of the animals in this way should therefore prevent the occurrence of thyroiditis. Suspensions of 1 x 108 spleen cells, of thymocytes, of lymph node cells and of bone marrow cells from normal syngeneic rats were therefore injected intraperitoneally or intravenously either in divided doses after each irradiation or as a single shot shortly after the final irradiation (Fig 5). The efficacy of these different cell preparations on the

9

Section of Enidocrinology

875

Histology, Serology etc.

Tx

X

200 rad X X

X

II

I

u

l

l

u-

9 Weeks after Fig 5 Schedulefor the reconstitiuttion birth of Tx-X rats with cells. (Reproduicedfrom Penhale et al. 1976 by kindpermission)

lynmphoid

I x lol Lymphoid cel Is

i.p. or i.v. RECONSTITUTION OF Tx-X RATS WITH LYMPHOID CELLS (I.P)

Mean

pathoogy index ± SEM

Mean

antibody titre

(1092)

± SEM -

I Controls (Tx-X)

I Thymocytes IV Lymph node cells V Bone marrow cells

m Spleen cels

Fig 6 .The effectiveness of 1 x 108 normalsyngeneic lymphoid cells given intraperitoneally according to the schedule shown in Fig 5 in preventing the development of antibodies to thyroglobulin and of thyroiditis. It is to be noted that neither thymocytes nor bone marrow cells reduced the incidence ofthyroiditis or the titre of thyroglobulin antibodies, but that both thyroiditis and thyroglobulin antibodyformation were preventedfrom developing when lymph node cells or spleen cells were used

development of thyroglobulin antibodies in the serum and of the histological appearance of thyroiditis at eight weeks after the final irradiation is shown in Fig 6. When given intraperitoneally thymocytes had no significant effect either on the development of thyroglobulin antibodies or on thyroiditis, although when given intravenously they did have a relatively weak inhibitory effect. By contrast, suspensions of lymph node cells or of spleen cells were highly effective in preventing

thyroid autoimmunity when given either intraperitoneally or intravenously, lymph node cells being rather more effective than spleen cells in so far that smaller numbers of lymph node cells

ould prevent the onset of thyroid autoimmunity comparison with the number of spleen cells equired. It would appear that thymocytes by hemselves are relatively ineffective in reconstitutng Tx-X rats but that thymus-processed lymphoytes require to mature in peripheral lymphoid rgans before developing suppressor cell function. lone marrow cells, if anything, augmented the utoimmune thyroiditis but the difference from ontrol Tx-X animals was not statistically signi[cant. Complete abrogation of the autoimmune reponses was only possible when cells were adninistered within a short time of the final dose of rradiation. Moderate thyroid damage was again een if transfer was delayed for 14 days postrradiation. At 28 days, reconstitution had no Ifluence on the development of the autoimmune esponses. Preliminary characterization studies Ising an anti-T-cell serum and fractionation of ymph node cells on a linear Ficoll gradient sugested that the autoregulatory cell is a large T-cell Penhale et al. 1976). Tx-X PVG/c rats also develop antinuclear ntibodies and a proportion show oophoritis. In Jlation to the ovaries, however, it is not at the ioment clear what contribution irradiation has iade to the histological lesions as control experitents masking the ovaries from irradiation fiave ot yet been done. It is of interest that thyroiditis features so ,rominently in these Tx-X animals as thyroiditis ; the commonest of the organ-specific autonmune diseases in man. The concept that organ-specific autoimmune iseases arise from a relative deficiency in imtunological function involving the control techanisms, is compatible with the experience in tan of increasing thyroid autoimmunity with age [rvine et al. 1970) when one would expect the rnmunological system to show evidence of failing long with other systems. The animal model reviewed here provides a iay of analysing the sequence of events that leads ) the gross clinical picture and of studying subopulations of lymphocytes that have the ability n

10

876 Proc. roy. Soc. Med. Volume 69 November 1976 to restore normal immunological control in terms of recognizing the difference between self and non-self.

Acknowledgment: This work was supported by a grant from the Medical Research Council. REFERENCES Allison A C, Denman A M & Barnes R D (1971) Lancet i, 1 35 Irvine W J (1974)Proceedings of the Royal Society of Medicine 67, 548-555 Irvine W J, Clarke B F, Scarth L, Cullen D R & Duncan L J P (1970) Lancet ii, 163-168 Penhale W J, Farmer A & Irvine W J (1975) Clinical and Experimental Immnunology 21, 362-375 Penhale W J, Farmer A, McKenna R P & Irvine W J (1973) Clinical and Experimental Immunology 15, 225-236 Penhale W J, Farmer A, Urbaniak S J & Irvine W J (1975) Clinical and Experimiental Immunology 19, 179-191 Penhale W J, Irvine W J, Inglis J R & Farmer A (1976) Clinical and Experimental Inmmunology 25, 6-16

The following papers were also read:

Growth Hormone Deficiency Following Treatment of Acute Leukeemia in Children Dr S M Shalet, Dr C G Beardwell, Dr P H Morris Jones and Dr D Pearson (Christie Hospital & Holt Radium Institute, Manlchester) The Use of Continuous Blood Sampling and Time Series Analysis in Endocrine Research Dr B W Ellis, Mr N J Randall, Mr A J Becket and Professor H A F Dudley (St Mary's Hospital Medical School, London)

Production Rates of Cortisol, 11-Deoxycortisol, Corticosterone, Deoxycorticosterone and Aldosterone in 11-/-Hydroxylase Deficiency Dr 0 M Edwards, Dr J M Galley, Dr I H Mills and Dr A D Tait (Department ofMedicine, Addenbrooke's Hospital, Cambridge, CB2 2QQ) The Effect of ACTH and Bromocriptine on the Plasma Levels of 18-Hydroxycorticosterone and Aldosterone Dr C R W Edwards, Dr V I Martin, Dr M 0 Thorner, Dr P A Miall, Dr E A S Al-Dujaili and Dr G M Besser

(St Bartholomew's Hospital, London) The Effect of the Anti-estrogen Tamoxifen on Hormonal Responses to LHRH in the Male Dr K J Willis, Dr W R Butt and Dr D R London (Queen Eli-zabeth Hospital and Women's Hospital, Birmingham)

Meeting 24/25 February 1976 with the Society for Endocrinology The subject was The Gut as an Endocrine Organ. Abstracts of papers presented appeared in Journal ofEndocrinology, 1976, 70, 1 P-15P.

Meeting 28 April 1976 The following cases were presented:

Autoimmune Thyroid Disorders in Identical Twins: (1) Ophthalmic Graves' Disease (2) Hashimoto's Thyroiditis Dr F Clark (Newcastle General Hospital, Newcastle utpon Tyne) REFERENCE Thornham J R, Nutt J E & Clark F (1976) Postgraduate MedicalJournal 52, 285

Unusual Case of Ph.eochromocytoma Dr Peter Daggett (for Professor S J G Semple) (Middlesex Hospital, London) Diabetes Mellitus with Diminished Insulin Requirements Due to Partial Hypopituitarism in a Patient with Pernicious An&emia, Ophthalmic Graves' Disease and Myasthenia Gravis Dr R N Clayton, Dr D R London and Dr P A Thorn (Qlueen Elizabeth Hospital, Birmingham) PPoma Dr S R Bloom, Dr P I Reed, Dr J M Polak, Dr T E Adrian and Dr W A Davies (Royal Postgraduate Medical School,

London) REFERENCE Polak J M, Bloom S R, Adrian T E, Heights P, Bryant M G & Pearse A G E (1976) Lancet i, 328-330

Gigantism Associated with Normal Growth Hormone and Increased Somatomedin Levels Dr A Howell (introduced by Professor R Hoffenberg) (Queen Elizabeth Hospital, Birmingham) Hirsutism Due to Adrenal 3-/3 Hydroxysteroid Dehydrogenase Deficiency? Dr D F Child and Dr D C Anderson

(Manchester Royal Infirmary, Manchester)

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Autoimmune thyroiditis in T-cell-depleted rats.

Volume 69 November 1976 7 873 Section of Endocrinology President Professor Reginald Hall Meeting 24 March 1976 Short Papers Autoimmune Thyroiditi...
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