Kevin J. Lafferty

T-Lymphocyte Clone Specific for Pancreatic Islet Antigen

A cloned T-lymphocyte line, BDC-2.5, was derived from a nonobese diabetic (NOD) mouse and has been found to exhibit specificity for islet cell antigen in vitro and in vivo. This clone is a CD4+ T-lymphocyte that proliferates and makes lymphokine in response to islet cell antigen- and NOD antigen-presenting cells. In an in vivo transplantation system in which islet grafts were made in the presence or absence of the BDC-2.5 T-lymphocytes, it was found that incorporation of the islet-specific T-lymphocytes into the graft site resulted in complete destruction of the transplanted tissue. Similar grafts made with pituitary tissue were not affected by the T-lymphocyte clone. These results suggest that the islet-specific T-lymphocytes mediate islet destruction in a tissue-specific manner.

The Th1/Th2 balance in autoimmunity

The study of autoimmune disease in the context of T-helper type 1 (Th1) and T-helper type 2 (Th2) CD4+ T-cell responses demonstrates that the relative contribution of either T-cell type to the development of a particular autoimmune response can influence whether or not this response leads to clinical disease. Moreover, this influence can be quite different depending on whether the particular disease process is cell mediated or antibody mediated. Recent studies have demonstrated that the development of Th1 and Th2 responses may be significantly influenced by the costimulatory molecules recognized by responding CD4 T cells, and by other undefined factors in the genetic background. It has also been demonstrated that autoreactive Th2 CD4+ cells can regulate the activity of disease-causing Th1 CD4+ T cells in vivo. Control of autoimmune disease may thus be achieved by procedures that regulate the relative contribution of Th1/Th2 CD4 T cells to an autoimmune response.

Effect of organ culture on the survival of thyroid allografts in mice.

Mouse thyroid can be maintained in organ culture for 4 weeks. Uncultured BALB/c thyroid is rejected 10–15 days after transplantation under the kidney capsule of H-2 disparate recipients (C57BL, CBA). Organ culture of thyroid tissue prior to transplantation prolongs allograft survival. This prolongation of graft survival increases with increasing time in culture and 80–90% of BALB/c thyroids maintained in culture for 26 days survive in allogeneic CBA recipients for a 60− to 70-day test period. These allografts show normal function as measured by 125I uptake, and show no histological evidence of chronic rejection. Cultured allografts can be rejected if the hosts immune-system is stimulated with viable leukocytes of donor origin. Host animals carrying a functioning allograft are not tolerant of donor tissues and will reject a second uncultured allograft from the same donor strain.

Role of Lymphokine and Antigen in the Control of Specific T Cell Responses

Our interest in the process of T cell activation derives from a more general concern with the mechanism of the allograft reaction. In this review we will show how the study of allogeneic interactions led to the development of a two-signal model for T cell activation, in which both antigen and a hormone-like molecule produced by lymphoreticular cells (lymphokine) are seen to play an equally important role in the process of T cell activation. We will then go on to consider experimental evidence that supports the model, and to examine cellular requirements for the production and release of lymphokine from lymphoreticular cells.

Autoimmune Diabetes in NOD Mouse Is L3T4 T-Lymphocyte Dependent

Cultured BALB/c islets fail to function when transplanted into diabetic nonobesediabetic (NOD) mice; such grafted tissue is rapidly destroyed by disease recurrence. The cellular requirements for this graft damage are unclear. This study was designed to investigate the role of the L3T4+ T-lymphocyte subset in disease recurrence in the NOD mouse. L3T4+ T-lymphocytes were depleted by the in vivo administration of the L3T4-specific monoclonal antibody GK1.5. This treatment reduced the level of L3T4+ T-lymphocytes from an initial 43% of the peripheral blood lymphocytes to 4%. L3T4 levels remained at this low level for ∼2 wk after withdrawal of GK1.5 treatment, after which the L3T4 levels slowly began to increase in the periphery. Grafting of cultured BALB/c islet tissue into GK 1.5-treated diabetic NOD mice resulted in a rapid return to normoglycemia that persisted for 2-4 wk. The gradual return to the hyperglycemic condition roughly correlated with the reappearance of L3T4+ T-lymphocytes in the peripheral circulation. From these findings we conclude that the disease process in the NOD mouse is L3T4 T-lymphocyte dependent.

Successful Allotransplantation of Mouse Pancreatic Islets to Nonimmunosuppressed Recipients

Pancreatic islets from BALB/c (H-2d) mice are rejected within 14 days of transplantation to the kidney capsule of allogeneic, CBA/H (H-2k) recipients. Cyclophosphamide pretreatment of the islet donor reduced the intensity of the allograft response, and these islets undergo a more chronic rejection process. Islets from cyclophosphamide-pretreated donors can be cultured in a gas phase of 95% O2 and 5% CO2, provided the islets are aggregated into clusters of about 50 islets. After a culture period of 7–12 days, the islet tissue was transplanted to normal allogeneic recipients, where the tissue elicited little or no allograft response over a 3-mo observation period.

Combined Treatment With Nicotinamide and Desferrioxamine Prevents Islet Allograft Destruction in NOD Mice

Nonobese diabetic (NOD) mice get spontaneous diabetes with clinical and pathological manifestations similar to those seen in human type I diabetes. NOD mice will destroy transplants of treated allogeneic islet tissue by a recurrence of the disease process that destroyed the original islet tissue. This may be prevented by treatment of the animals with combined desferrioxamine and nicotinamide. Transplanted animals become normoglycemic and remain so for the duration of the treatment. This suggests that oxygen-derived free radicals may be involved in islet damage in spontaneous diabetes.

Inhibition of T-cell activity by cyclosporin A.

Cyclosporin A (CyA) inhibits early events in the T‐ccll response. It strongly suppresses the activation of naive T cells by IL1 or IL2 and alloantigen. CyA exerts a selective effect on activ ated T cells, It inhibits the ability of these cells to release IL2 in response to antigen or mitogen restimulation, at concentrations that have no effect on the ability of these same cell populations to respond to IL2 by proliferation. The specific effects of CyA are not limited to T cells, however, and this drug will inhibit IL1 production by lipopolysaccharide W‐stimulated PU5‐IR cells.

Cellular changes in cultured mouse thyroid glands and islets of langerhans.

Islets of Langerhans cultured 7 days in vitro no longer contained any capillary endothelial cells, but their endocrine cells remained ultrastructurally normal up to 14 days. Vascular endothelial cells were also lost from cultured thyroid lobes, but more slowly. Thyroid endothelium was readily identified after 7 days of culture, although many cells appeared to be degenerating, and a few degenerating endothelial cells were still present after 14 days in culture. Erythrocytes and leukocytes in the lumina of thyroid vessels were observed to degenerate at about the same rate as the endothelial cells, while those in islet capillary lumina were largely washed out during isolation of the islets. Thyroid lymphatic endothelium and the numerous adipose cells present in this tissue also degenerated during the culture period. Follicle epithelial cells remained viable throughout the culture period, but the number of colloid droplets and endocytic vesicles they contained was markedly decreased. Thyroid fibroblasts remained viable and appeared to enlarge and accumulate dense granules during culture. These cells were a prominent feature of thyroid lobes after 14 days of culture. Parathyroid tissue associated with the thyroid lobes showed viable endocrine cells but a loss of vascular endothelium after 14 days in culture. The loss of blood leukocytes and vascular endothelial cells is probably the major factor in the altered behavior of thyroid and islet allografts after culture in vitro.

Involvement of O2 radicals in «autoimmune» diabetes

Spontaneous diabetes in the non‐obese diabetic (NOD) mice is a CD4 T cell‐dependent process. We have suggested that specific β cell destruction results from free radical production at the site of islet inflammation; oxygen radicals are produced by activated inflammatory cells. We reported here that in vivo treatment of spontaneously diabetic NOD mice with the enzyme superoxide dismutase (2000 U for seven injections) and catalase (40 000 U for seven injections) protects islet tissue from disease recurrence following transplantation into spontaneously diabetic mice. Similar results were obtained when animals were treated with either enzyme alone. This effect was dose‐dependent and little protection was observed when the dose of enzyme was reduced four‐fold. These results indicate that oxygen metabolites, specially superoxide and hydrogen peroxide, are directly involved in the pathogenesis of immunology mediated diabetes.