Role of IL-1 in the activation and inactivation of human T-cell clones: Relevance to rheumatological disease

Interleukin-1 has a key role in the initial activation of T cells. However, its role, once T cells are fully activated, is not known. Human T-cell clones, driven with antigen and antigen-presenting cells once a week, and twice weekly with interleukin-2, are the most activated T cells known. We thus tested whether IL-1 was necessary for the activation of T-cell clones, using mouse L cells (incapable of producing human IL-1) transfected with human HLA-DP genes. No requirement for exogenous IL-1 was detected for induction of proliferation. In contrast to the lack of a requirement for IL-1 in T-cell activation, T-cell tolerance, the state of antigen-specific antigen-induced unresponsiveness, was partly blocked by IL-1 indicating that these cells can still respond to IL-1 in the appropriate circumstances. Blockage of tolerance induction by IL-1 may be one of the mechanisms underlying the maintenance of the autoimmune process.