Mediation of immunity to Eimeria vermiformis in mice by L3T4+ T cells.

Immunity to infection with Eimeria vermiformis was transferred in NIH mice by both the nylon wool-adherent (B-cell-enriched) and nonadherent (T-cell-enriched) fractions of lymphocytes (spleen and mesenteric lymph node) taken from infected donors. Transfer was more variable with the adherent fraction, and when contaminating T cells were removed by treatment with anti-Thy1 monoclonal antibody (MAb) and complement, this fraction lost all protective activity. The protective effect of T-cell-enriched populations of mesenteric lymphocytes was abrogated by treatment with anti-L3T4 MAb and complement in vitro before transfer or by opsonization with this MAb in vitro before intravenous inoculation into recipients. Similar treatments of cells with anti-Lyt2 MAb did not have this effect, confirming that Thy1+ L3T4+ cells mediate the adoptive transfer of immunity to E. vermiformis. Thy1+ L3T4+ cells were also shown to limit the replication of E. vermiformis in primary infections: mice depleted of this subset (by thymectomy followed by intravenous injection of anti-L3T4 MAb) passed greater numbers of oocysts over a longer period of time than did mice similarly depleted of Lyt2+ cells.