IN-VIVO T-CELL RESPONSE TO VIRAL SUPERANTIGEN - SELECTIVE MIGRATION RATHER THAN PROLIFERATION

Superantigens induce T cell activation and proliferation in vitro, and some also induce cell activation in vivo. MMTV(SW) is an infectious m ouse mammary tumor virus (MMTV) encoding a superantigen with the same V beta specificity as Mls-1(a) (Mtv-7), which induces a strong local r esponse in vivo. Injection of MMTV(SW) into mouse footpads leads to ac cumulation of superantigen-reactive T cells (V beta 6(+)CD4(+)) and B cells in the draining lymph nodes (LN). We investigated the kinetics o f this cell accumulation by measuring cell activation (blastogenesis, CD25 and CD69 expression), cell migration (using syngenic FITC-labeled CD4(+) cells and L-selectin detection), and cell proliferation (using in vivo labeling with bromodeoxyuridine). Specific T cells selectivel y migrated to the draining LN. Accumulating V beta 6(+)CD4(+) T cells were large CD69(+) cells, but remained CD25 negative and showed down-r egulated L-selectin expression. Their DNA synthesis rate, studied by p ulse labeling and continuous administration of bromodeoxyuridine, was increased, but remained too low to explain the draining LN hyperplasia . These data show that the local T cell response to MMTV(SW) mainly co nsists of selective migration followed by local activation of reactive T cells, and that cell proliferation is only a minor component of the response. By contrast, the optimal dose of staphylococcal enterotoxin B that, nevertheless, leads to a lower reactive T cell accumulation i n the draining LN induces a very high proliferation rate.