Evaluation of B-cell, T-helper-cell, and T-suppressor-cell function in patients with Graves' disease before and after treatment with anti-thyroid drugs

CD5-positive and CD5-negative rheumatoid factor-secreting B cells in IgA nephropathy, rheumatoid arthritis and Graves' disease

The relative contributions of CD5+ and CD5- B-cells in production of rheumatoid factors (RF) was evaluated in polyclonally activated B-cells from patients with IgA nephropathy (IgAN), rheumatoid arthritis (RA) and Graves' disease (GD). In IgAN and RA, diseases in which RFs are believed to be involved in pathogenesis, there were 10- and 4-fold decreases respectively in CD5+ IgG-RF-secreting B-cells compared with controls. Furthermore, the number of CD5- IgG-RF- and IgA-RF-secreting B-cells were increased 12- and 14-fold in IgAN and 9- and 4-fold in RA. Such abnormalities were not apparent in GD, in which RFs have not been implicated in pathogenesis. These findings are compatible with the concept of CD5+ RF-secreting B-cells normally acting to prevent production of potentially pathogenic RFs by CD5- B-cells. When IgAN or RA patients' B-cells were activated in the presence of control instead of autologous CD4+ cells, numbers of RF-secreting CD5- B-cells were reduced to the levels seen with control B-cells plus control T-helper cells. Presumably lymphokine secretion profiles of T-helper cells would be important in determining whether CD5+ or CD5- B-cells are activated to secrete RFs, and perhaps therapeutic manipulation of these profiles could restore normal activity of CD5+ B-cells in IgAN and RA.

Analysis of impaired in vitro immunoglobulin synthesis in rheumatoid arthritis

Decreased immunoglobulin production in pokeweed mitogen driven lymphocyte cultures has been reported in rheumatoid arthritis (RA). Here various activators and experimental designs have been used to determine the contribution of B cells, T cells, or monocytes to this low response. Sixty patients with RA and paired controls were studied at the onset of disease and again six months later. Concentrations of IgA, IgG, and IgM in cultures of RA peripheral blood mononuclear cells stimulated with thymus dependent activators were already decreased at the onset of the disease. Six months later RA mononuclear cells produced even lower concentrations of immunoglobulin. In contrast, stimulation with a T cell independent activator showed that RA B lymphocytes had retained normal potential to synthesise immunoglobulin. Poor helper function was indicated by costimulation experiments and cultures of mixed mononuclear cells from patients and controls. This notion was supported also by the fact that phytohaemagglutinin induced interleukin-2 production by RA mononuclear cells was less than half of the control values. Nonspecific suppressor activity was similar in RA and controls. Monocyte functions were normal when tested by addition of indomethacin or 2-mercaptoethanol to the mitogen activated cultures. The defect in mitogen stimulated immunoglobulin production in vitro of RA mononuclear cells thus was more pronounced with time and probably reflects impaired mediator associated help in the differentiation of B lymphocytes into immunoglobulin secreting cells.

The immunoregulatory disturbance in autoimmune thyroid disease

There is now considerable evidence for a genetically induced antigen-specific defect in suppressor T lymphocytes as the basis for AITD, derived from several laboratories and via different types of experimental techniques. In addition, there is now evidence for additive effects on reducing generalized suppressor T lymphocyte numbers and/or function by environmental factors as well as hyperthyroidism itself, and these effects would be superimposed upon the organ-specific defect. Such effects on generalized suppressor T lymphocyte numbers may act as precipitating and self-perpetuating factors, in Graves' disease at least. Presentation of the antigen by the thyroid cell via HLA-DR expression on its membrane does occur as a result of interferon gamma production by T lymphocytes. This in turn appears to be secondary to the initial specific immune assault and is not a primary inductive step. However, it may be important as an amplifying intermediate factor but cannot perpetuate the process in the absence of the underlying immune disorder. There is, however, no evidence for an underlying antigenic abnormality or stimulus in human autoimmune thyroid disease, and the initiating event would appear to be due to perturbation of the generalized immune system superimposed on the organ-specific abnormality. Variations in the serological and clinical expression of AITD would appear to depend on the severity of the original organ-specific disturbance in suppressor T lymphocyte function, plus the added factor of environmental influences playing upon generalized suppressor T lymphocyte function and numbers. Remissions in Graves' disease brought about by antithyroid drugs may well be via their effect on modulating the thyroid cell activity; this will then reduce thyrocyte-immunocyte signalling, allowing remission to occur in those patients with a partial organ-specific defect in suppressor T lymphocytes.

Autoimmune thyroid disease: immunological, pathological, and clinical aspects

Autoimmune thyroiditis, most notably Hashimoto's thyroiditis, appears to be increasing in prevalence and is now more easily detected by sensitive laboratory tests and more invasive procedures such as fine needle aspiration. During the last decade, marked progress has been made in the understanding of these diseases. There is a greater awareness of the interaction between the humoral and cell-mediated arms of the immune system in autoimmune thyroiditis. Recent studies implicate a subpopulation of suppressor T lymphocytes which have an antigen-specific defect, resulting in their suboptimal interaction with the helper T lymphocytes and subsequent autoimmune manifestations. There is some evidence that thyroid epithelial cells which inappropriately express HLA-DR may enhance presentation of thyroid antigens to the immune system, possibly significant in the initiation or enhancement of the autoimmune response. The presence of various antithyroid autoantibodies allows the use of laboratory assays to confirm the clinical diagnosis and predict the results of treatment. There appears to be predisposing genetic factors in the development of autoimmune thyroiditis, with some geographical and racial differences. Environmental factors, most notably dietary intake of iodine, have also been implicated in the pathogenesis of Hashimoto's thyroiditis. Several animal models have been developed addressing such issues. Ongoing studies in the areas of postpartum thyroiditis and childhood thyroiditis are helpful in clarifying their relationship with Hashimoto's thyroiditis. Graves' disease and postpartum thyroiditis are being investigated as possible causes of postpartum depression. The association of Hashimoto's thyroiditis and carcinoma of the thyroid gland is still controversial, but its relationship with malignant lymphoma is now well accepted. Thus, although the pathogenesis of autoimmune thyroiditis remains elusive, there has been significant refinement of the clinical diagnosis, and immunological abnormalities of specific intrathyroidal lymphocytes have been identified. Hopefully, these new areas of knowledge will assist in the treatment of these diseases and in the prevention of the development of malignant lymphomas of the thyroid gland.

Immunohistochemical characterization of intrathyroid lymphocytes in Graves' disease. Interstitial and intraepithelial populations

The phenotypic cell surface markers of the lymphocytes present in thyroid tissue from four patients with Graves' disease were quantitatively analyzed using the avidin-biotin immunoperoxidase technique. As control specimens, normal perinodular tissues from three patients who had benign thyroid nodules resected were also studied. In contrast to normal thyroid tissue, which contained very few T cells and no B cells, thyroid tissue of all four patients with Graves' disease contained a lymphocytic infiltrate, and this could be divided into two populations of lymphocytes. The first population was located in the follicular epithelium and expressed a cytotoxic-suppressor T cell marker (Leu2a). On the average, these cells were 4.2 times as numerous in Graves' tissues as in normal tissues (p less than 0.05). Most of these cells did not express Leu1, a pan-T cell marker. The second population was found in the interstitial tissues, often within lymphoid aggregates, and 70 to 83 percent of the cells expressed Leu1. The majority of these cells expressed a helper-inducer T cell marker, Leu3a; Leu3a/Leu2a ratios within aggregates ranged from 1.9 to 2.1. The number of B cells present was small, ranging from 5.8 to 12.1 percent of the interstitial lymphocytes. These findings are consistent with the involvement of both helper-inducer and suppressor-cytotoxic T cells in a localized autoimmune reaction directed, at least in part, against the thyroid follicular epithelial cells.