Class II Hla-Dr Antigens on Non-Autoimmune Human Thyroid Cells Stimulate Autologous T Cells with High Suppressor Activity

Human autoimmune thyroid cells “spontaneously” express MHC-class II antigens. These antigens have been assumed to trigger thyroid-specific helper T cell clones, leading in turn to the expansion of thyroid autoantibody-secreting B cells. Thyroid cells derived from non-autoimmune subjects do not express MHC-class antigens, but these can be readily induced with -γ-interferon. We have addressed the issue of whether it is sufficient for normal thyroid cells to bear class II antigens in order to trigger autologous T cells. We found that non-autoimmune thyrocytes expressing DR antigens fail to stimulate autologous resting T cells. However, proliferative activity and interleukin-2 secretion were observed when fresh T cells were first triggered by autologous non-T cells and then incubated with thyrocytes. More CDg than CD4, cells proliferated in the T:thyrocyte cultures, but CD4 cells were necessary for the proliferation and interleukin-2 secretion. Addition of antibodies to thyroglobulin or to DR antigens inhibit...