Insulin‐specific T cell help to TNP‐specific B cells requires activation via the antigen T cell receptor

Abstract

In the present study, the production of large numbers of insulin (Ins)-specific, H-2-restricted T helper (Th) cell clones is described. Among 148 clones analyzed, 121 clones had Th cell function, and these were divided into 75 Ins-specific Th cell clones and 52 autoreactive clones. The 148 clones were isolated from Ins-specific T cell lines produced by in vitro stimulation of T lymphocytes from (b X d)F1 mice immunized with Ins 7, 14, 32 or 56 days before. The following characteristics were tested with regard to the Th cell clones: restriction specificity and antigen requirement for optimal help or interleukin 2 (IL2) production. No differences in these characteristics were found among clones originating from day 7, 14, 32 or 56 T cell lines. A preference for H-2b as restriction element and an antigen concentration of about 0.01 microgram trinitrophenylated (TNP)-Ins/ml for optimal help were general traits. Optimal IL2 release is not yet obtained with 100 micrograms TNP-Ins/ml. Thus, the antigen requirement for optimal help and IL2 release differs by a factor 10(4) at least. Certain twice-cloned Th cell lines were tested for IL2 production when stimulated with anti-Thy-1 monoclonal antibodies (mAb). All clones analyzed were stimulated by mAb H155 but not with mAb H140 nor with mAb against Lyt-1, L3T4, LFA-1 or H-2K/D molecules. Therefore, we determined whether TNP-conjugated H155 mAb would mediate Th cell-B cell collaboration as well as TNP-Ins. The results with nine different Th cell clones and six different TNP-conjugated mAb used in a 10(7)-fold concentration range showed that Th cell clones have to be triggered via the T cell receptor for expression of helper function to B cells. Thus, though IL2 gene activation, synthesis or release apparently can be activated via at least two pathways: T cell receptor or Thy-1, it seems that activation of the genes responsible for synthesis and release of the helper factors, which ensure antigen-specific B cell proliferation and differentiation, needs Th cell-B contact mediated via the antigen-specific T cell receptor.