DETECTION OF PRECURSOR T-H CELLS IN MESENTERIC LYMPH-NODES AFTER ORALIMMUNIZATION WITH PROTEIN ANTIGEN AND CHOLERA-TOXIN

We have characterized the earliest antigen-specific T-h cells in murin e mesenteric lymph nodes (MLN), following oral immunization with the h en egg lysozyme (HEL) as antigen and cholera toxin (CT) as adjuvant. W e did this by analyzing in vitro proliferation and cytokine production in response to HEL by the MLN T cells. MLN cells taken 5 days after a single oral immunization with HEL and CT provided the earliest source of proliferating HEL-specific T cells. This proliferation was complet ely inhibited by anti-lid, but not inhibited by anti-IL-4 antibody. IL -2 protein was detected in culture supernatants but not IL-4 using ELI SA or bioassays. IL-4 mRNA was not found in responding cells using RT- PCR. Some of the day 5 MLN cultures produced IFN-gamma in response to HEL, but isolated T cells from the same MLN did not. Exogenous IL-4 al one did not stimulate day 5 MLN T cells, but IL-4 did synergize with H EL to induce a large proliferative response. The data indicate that th e HEL-specific CD4 T cell pool in MLN 5 days after oral immunization i s composed of undifferentiated precursor T-h cells. These cells have t he potential for IL-2 production and IL-4R expression upon re-stimulat ion in vitro.