Patricia Hutchings

Infection with Schistosoma mansoni prevents insulin dependent diabetes mellitus in non‐obese diabetic mice

The spontaneous development of insulin dependent diabetes mellitus in non‐obese diabetic (NOD) mice has been shown to be mediated by a Th1 response against beta cell antigens. It is known that in murine models of Schistosoma mansoni infection, egg production is associated with a switch from a Th1 to Th2 response. This subsequent dominance of a Th2 response in S.mansoni infected mice has been shown to influence the response to other infectious agents or antigens. We therefore determined whether infection with S.mansoni could influence the spontaneous incidence of insulin dependent diabetes mellitus (IDDM) in NOD mice. Infection with this helminth significantly reduced the spontaneous incidence of IDDM. IDDM was also prevented by injecting parasite eggs alone. Because until relatively recently humans might expect to succumb to a variety of infectious agents, the current freedom from infection might permit the expression of a genetic predisposition to autoimmune pathology and be responsible for the increased incidence of IDDM.

The detection and enumeration of cytokine-secreting cells in mice and man and the clinical application of these assays

An in vitro assay for the detection and enumeration of mouse and human cytokine-secreting cells is described and some ways in which it may be used diagnostically are indicated. The assay is an extension of the ELISA plaque assay or ELISPOT assay and uses pairs of antibodies to capture and then visually develop secreted lymphokines. In this way, it is possible to enumerate the specific cytokine-secreting cells. This assay may provide a valuable tool in the clinical investigation of the mechanisms of disease development and tissue destruction.

The involvement of Ly 2+ T cells in beta cell destruction

The non-obese diabetic (NOD) mouse is considered to be a good model of human Type I diabetes mellitus. Both sexes develop insulitis starting at about 6 weeks of age, and onset of diabetes follows at about 30 weeks in females, but later and much less frequently in males. In some mice (but not all) infiltration of the islets leads to selective destruction of insulin-producing beta cells, which is marked by clinically overt diabetes and is thought to be an autoimmune response mediated by T cells. Both L3T4+ and Ly2+ cells have been implicated in the destructive process and we have used an in vivo transfer system, together with histological studies on the pancreas, to demonstrate the essential role played by Ly2+ T cells in the destruction of beta cells in diabetic mice.

The forces driving autoimmune disease.

There are two classes of autoimmune disease, organ-specific and non-organ specific or systemic. That cells producing autoantibodies are selected by antigen is strongly suggested by the presence of mutations and high affinity antibody. T-cells are pivotal in all forms of autoimmunity as evidenced by the therapeutic benefit of anti-T-cell monoclonals such as anti-CD4, and the frequent development of high affinity IgG autoantibodies. The production of anergic T-cells by the use of non-depleting anti-CD4 in the presence of antigen is discussed with particular reference to its potential for immunological intervention in autoimmune disease. It is possible to identify T-cell epitopes in organ-specific autoimmunity using pathogenic T-cell clones or hybridomas to identify the peptide sequences which are reactive. Antigen-specific therapy may ultimately be based on such peptide epitopes. The specificity of the T-cells in systemic autoimmunity is still obscure, but there is some evidence that reactivity with certain germ-line idiotypes can lead to the development of systemic autoimmunity. The possibility of stimulating B-cells specific for auto-antigens such as DNA becomes feasible if a complex of antibody and DNA is taken up by these specific B-cells and processed idiotype is presented to T-helpers specific for those idiotype epitopes. Evidence is presented that there may be pre-existing defects in the target organ in certain organ-specific disorders, and the evidence for a glycosylation defect in the IgG in patients with rheumatoid arthritis is explored. It is noted that the spouses of probands with rheumatoid arthritis is explored. It is noted that the spouses of probands with rheumatoid arthritis also tend to have this glycosylation defect and this raises the possibility of an effect due to an environmental factor, such as a microbial infection. Molecular mimicry of autoantigens by microbes can stimulate autoreactive cells by their cross-reactivity. It is emphasized that cross-reaction which gives rise to the priming of autoreactive T-cells could give rise to the establishment of a chronic autoimmune state. In animals with normal regulatory immune systems, such induced autoimmunity is ultimately corrected and it is only in animals where there are defects in regulation, that autoimmunity persists. Thus, there are many factors giving rise to autoimmunity, and the diseases are rightly regarded as multifactorial in origin.

Tolerance to IDDM Induced by CD4 Antibodies in Nonobese Diabetic Mice is Reversed by Cyclophosphamide

IDDM can be induced in nonobese diabetic (NOD) mice in several ways, including high doses of cyclophosphamide and transfer of diabetic spleen cells to sublethally irradiated recipients. It has previously been established that transferred diabetes can be prevented by treatment with a nondepleting CD4 monoclonal antibody; however, we report herein that cyclophosphamide-induced diabetes also can be prevented using this antibody. The protection induced by CD4 monoclonal antibody to transferred diabetes is maintained for a long period after cessation of antibody treatment. However, cyclophosphamide can abrogate this induced tolerance and we report that this abrogation does not require new T-cells. During the course of the experimental work described, we observed that the thymus had a suppressive effect on the expression of transferred disease. Mice that were depleted of their peripheral T-cells showed a doubling of the time for disease expression if they were euthymic, compared with thymectomized mice.

Autoantigens in thyroid diseases

SummaryThe autoantigens involved in autoimmune thyroid disease have now been extensively characterised, and the autoantibodies they evoke provide important aids to diagnosis, leading to early treatment of thyroid autoimmunity. The next stage in the puzzle is to determine towards which epitopes on the autoantigens the immune response is directed. We have already come a long way in the identification of immunodominant epitopes and have been able to identify one T cell epitope which has pathogenic capabilities. Identification of other T cell and B cell epitopes will help us understand the cell-mediated and humoral responses in greater detail and in time lead to more specific therapeutic intervention. A greater understanding of the mechanisms underlying one particular autoimmune disease will give us insights into other diseases, due to the belief that there may well be common underlying defects that, due to a multitude of factors, manifest as different diseases. The susceptibility factors in autoimmune thyroidits and autoimmune disease in general are very complex. A greater understanding is required of HLA associations and how particular peptides are presented in vivo. Are susceptible MHC types the ones capable of presenting the pathogenic peptides? Our major T cell thyroiditogenic epitope contains a T4 residue which accounts for over half the molecular weight of the peptide. Its structure is large and consists of a double benzene ring structure with four iodine atoms. It will be interesting to see how such a peptide can be presented and which residues bind T cell receptor or MHC. In summary we can say that autoimmune disease is due to a cocktail of factors which all contrive to tip the delicate balance of the immune system into an autoimmune state. HLA association may play a role in conferring an enhanced ability to select from a restricted repertoire of pathogenic epitopes, those epitopes perhaps only becoming available for presentation after interaction with environmental agents, whatever they may be. Following this, the normal regulation of self presentation and tolerance mechanisms break down and autoimmunity supervenes.

Con-A-induced suppressor activity of lymphocytes distinguished by the presence or absence of the Fc receptor☆

Abstract Lymphocytes bearing a receptor for the Fc region of the IgG molecule (Fcγ + ) were separated from those lacking the receptor (Fcγ − ) by a two-step procedure involving adherence to antibody-coated bovine erythrocyte monolayers followed by rosetting with antibody-coated bovine erythrocytes and separation on a Ficoll-Metrizoate gradient. Using this procedure, we confirmed previous work showing that cytotoxicity induced by the graft versus host reaction was mediated by cells bearing the Fc receptor. Separated cell populations were cultured with Con-A for 48 hr and then tested for their ability to mediate nonspecific suppression of both primary and secondary responses to SRBC in vitro . Suppressor cells were generated from both Fcγ + and Fcγ − cells following culture with Con-A. Therefore, no distinct functional differences in the ability to mediate nonspecific suppression can be attributed to subclasses of T-cells on the basis of possession of the FcR.

Current Molecular Approaches to Experimental Thyroid Autoimmunity

Autoimmune thyroiditis is characterized by mononuclear cell infiltration of the thyroid gland, with accompanying tissue damage, and associated cellular and humoral autoimmunity to thyroid antigens such as thyroglobulin (Tg) and microsomal antigen (for reviews see Bigazzi and Rose, 1985; Rose et al., 1981; Weetman and McGregor, 1984; Weigle, 1980; Wick et al., 1985). Since the seminal studies by Rose and Witebsky (1956) demonstrating the experimental induction of autoimmune thyroiditis, animal models have been used extensively, both in the search for clues to the etiology of human autoimmune thyroiditis and to investigate basic mechanisms in the regulation of autoimmunity. Thyroid autoimmunity arises spontaneously in a number of species (Bigazzi and Rose, 1975), but most work has concentrated on the obese strain chicken (Wick et al., 1982, 1985), buffalo rats (Bigazzi and Rose, 1975), and the diabetes-prone BB/W rat (Sternthal et al., 1981). Thyroiditis may also be induced experimentally in many species by injecting Tg and an appropriate adjuvant (Weigle, 1980). A different model of thyroiditis can be induced in rats by a combination of thymectomy and irradiation (Penhaie et al., 1973, 1975). Studies of these various models have provided valuable information regarding the mechanisms involved in thyroid autoimmunity. More recently, we and others have begun to use a variety of in vitro techniques to gain insight into the molecular basis of thyroid autoimmunity.

The Effect of MHC Encoding Transgenes on IDDM in NOD Mice

The nonobese diabetic (NOD) mouse provides an excellent animal model (1) of insulin-dependent diabetes mellitus (IDDM), an autoimmune disease in which the β cells of the pancreas are selectively and specifically destroyed by cells of the immune system. The spontaneous development of IDDM in NOD mice has been shown to be under polygenic control with major histocompatibility complex (MHC)-encoded genes playing a major role (2, 3). The MHC class II of the NOD consists of AαdAβg7 and EαbEβg7 heterodimers, thus resulting in the lack of expression of I-E in NOD mice (2) The Aβ chain of NOD mice contains several unusual amino acids in the first external domain including a serine at position 57 and a histidine at position 56 where most other mouse strains have an aspartate and a proline, respectively (4). Interest in the amino acid usage at position 57 stemmed largely from genetic studies of IDDM in humans, where it was observed that individuals protected from disease development tend to have a charged residue at this position in their DQβ chain (5). By analogy, therefore, it was proposed that serine 57 in NODAβg7 may predispose to development of IDDM in this strain.