Auto-immune disease. II. Pathology of the immune response

Integrated model of metabolism and autoimmune response in β-cell death and progression to type 1 diabetes

Progression to type 1 diabetes is characterized by complex interactions of environmental, metabolic and immune system factors, involving both degenerative pathways leading to loss of pancreatic β-cells as well as protective pathways. The interplay between the degenerative and protective pathways may hold the key to disease outcomes, but no models have so far captured the two together. Here we propose a mathematical framework, an ordinary differential equation (ODE) model, which integrates metabolism and the immune system in early stages of disease process. We hypothesize that depending on the degree of regulation, autoimmunity may also play a protective role in the initial response to stressors. We assume that β-cell destruction follows two paths of loss: degenerative and autoimmune-induced loss. The two paths are mutually competing, leading to termination of the degenerative loss and further to elimination of the stress signal and the autoimmune response, and ultimately stopping the β-cell loss. The model describes well our observations from clinical and non-clinical studies and allows exploration of how the rate of β-cell loss depends on the amplitude and duration of autoimmune response.

The why and how of thymocyte negative selection

The generation of T cell receptor (TCR) sequence diversity is the strength of adaptive immunity, yet is also the Achilles' heel. To purge highly self-reactive T cells from the immune system, generation of diversity has coevolved with a mechanism of negative selection. Recent studies have revealed new insights addressing the why and how of negative selection by examining situations in which negative selection has failed in human and animals models of autoimmunity. Both thymocyte extrinsic and intrinsic mechanisms are required to restrict the TCR repertoire to a non-autoreactive set. Negative selection also ensures that T cells emerge with receptors that are focussed on the peptide moiety of MHC-peptide complexes.

The role of prolactin in the pathogenesis of autoimmune disease

Prolactin has emerged in recent years as a major regulator of both the maturation and the function of lymphocytes. Prolactin abnormalities, which include elevated serum levels, decreased bioactivity, abnormal circadian rhythm, and exaggerated secretion after stimulation by TRH, are associated with various autoimmune conditions in humans. Some animal experiments and observations in humans indicate that proiactin has an important role in the pathogenesis of autoimmune disease. There are several mechanisms through which prolactin could promote the development of autoimmunity. It is concluded that prolactin abnormalities alone are not likely to cause autoimmunity, but rather additional regulatory defects are perhaps also required for disease to develop.

Hormones in self tolerance and autoimmunity: a role in the pathogenesis of rheumatoid arthritis?

Recent studies indicate that pituitary hormones play an important role in immunoregulation. The evidence that endocrine abnormalities are associated with, and may contribute to the development of autoimmune disease is reviewed and discussed. Patients suffering from rheumatoid arthritis show a number of endocrine abnormalities that indicate altered pituitary function. The decreased bioactivity of prolactin and possible inadequate glucocorticoid response to inflammation found in patients may have an etiological role in rheumatoid arthritis. The further clarification of the possible role of endocrine factors in the etiology of autoimmune disease is needed urgently.

Aging changes in lymphopoietic and myelopoietic organs of the annual cyprinodont fish, Nothobranchius guentheri

The thymus of aging annual, cyprinodont fish, Nothobranchius guentheri and Cynolebias adloffi begins to undergo senescent changes at approximately four months. At this time, the histopathology reveals increased amounts of connective tissue, epithelial cysts and myoid cells, but decreased numbers of thymocytes. At 12 months, of the 50 fish observed at 10 stages from day 15 and 1, 2, 4, 6, 8, 9, 10, 11, 12 months the maximum time of senescence, there was an increased incidence of tumors in the oral cavity, connective tissue, kidney and liver in all 5 fish. At least in the kidney, the malignant transformation was classified as nodular-type histiocytic lymphoma. It is of interest that development of these tumors occurs during peak senescent changes in the thymus, supporting the view that as fish age, accompanied by atrophy of the thymus, the immune system is less vigorous and there is an increase in the incidence of cancer.

Heterogeneity of precipitating antibodies in polymyositis and dermatomyositis. Characterization of the Jo-1 antibody system

Precipitating antibodies occurring in 26 "pure" polymyositis (PM) patients and 22 "pure" dermatomyositis (DM) patients were studied by double immunodiffusion using calf thymus nuclear extract and whole calf thymus extract. Seventeen of 26 (65%) PM sera and 13 of 22 (59%) DM sera showed positive reactions, and 18, 10, and 2 sera exhibited 1, 2, and 3 precipitin lines, respectively. Common specificities were established by immunodiffusion for the 11 PM and 6 DM sera with strong precipitin lines. These were classed into three groups of shared specificity and six reactions specific for individual sera. These 9 calf thymus antigens were shown to be different from the known soluble tissue antigens Sm, nuclear RNP, Ro, and La. A 600-fold purification of the most frequently appearing system designated Jo-1 was achieved and its clinical specificity for patients with PM syndromes was established.

Studies of human lymphocytes in the newborn and the aged

Proportions and absolute numbers of T and B lymphocytes were determined among 30 newborn infants and group of 77 elderly patients 60 to 95 years of age. Total lymphocytes in the cord blood of the newborn showed a distinct elevation in total numbers of T and B lymphocytes (p less than 0.005) as compared to that in blood from normal adult controls, reflecting the relative lymphocytosis of infancy. Proportions of cord blood T lymphocytes as reflected by the sheep cell rosette technic were considerable lower than those in lymphocytes from normal adult controls, however, proportions of cord blood T lymphocytes as determined by indirect immunofluorescence were not significantly different from those in controls. Old people showed a significant reduction in total numbers of lymphocytes (p less than 0.005) when compared with those in normal adult controls 18 to 51 years of age. Moreover, there was a significant increase in the relative proportions of peripheral blood B lymphocytes in the elderly although the absolute numbers of B lymphocytes in the elderly although the absolute numbers of B cells did not differ from those in younger controls. A significant decrease in total numbers of T cells as measured both by sheep cell rosettes and indirect immunofluorescence was recorded among older patients (p less than 0.001). In addition, there was a broad increment in the incidence of various autoantibodies (anti-nuclear, andi-IgG, antismooth muscle, antimitochondrial and antiparietal cell) among the old people studies. No direct correlation could be determined between relative B-cell percentage increase or T-cell decrease and the presence of various autoantibodies in individual patients. Diminution in total lymphocyte counts as well as absolute numbers of T cells in the elderly may provide the cellular basis for an increased susceptibility to neoplasia and infection.

Myositis in father and daughter

The occurrence of myositis in a father and his daughter is reported. The daughter's illness resembled childhood dermatomyositis and progressed to systemic involvement and death less than four years from the onset of symptoms. In the case of the father the illness followed the course of adult polymyositis and there was little evidence of systemic involvement. The immunological and genetic significance of the two cases is discussed.

Autoimmunity in a rural community

As part of a long term prospective study, sera from 3492 subjects, over 90% of the adult population of the rural Australian town of Busselton, were tested by indirect immunofluorescence for various autoantibodies, and by latex particle agglutination for rheumatoid factor. Autoantibodies were detected in 21·6% of all subjects and the overall prevalence increased with age in both sexes. A dip in the age prevalence curve of autoantibodies amongst subjects aged 75–80 years preceded a terminal sharp rise. The greater prevalence in females, 27·5%, than in males, 13·7%, was accounted for by autoantibodies to nuclei, gastric parietal cells and thyroid epithelial cells; the prevalence of smooth muscle antibody (SMA) and rheumatoid factor (RF) was similar in females and males, and the prevalence of SMA did not increase with age. Thus development of `age-sex dependent' autoantibodies, to gastric and thyroid antigens, may have a considerable genetic component, whereas the non `age-sex dependent' autoantibodies, SMA and RF, may have a considerable extrinsic component, e.g. infection. Autoantibodies were associated in two groups, a `nuclear' group and a `thyrogastric' group; these groups were neither positively nor negatively associated, implying independent genetic or other causes for their appearance.