CELLULAR-DYNAMICS AND CYTOKINE RESPONSES IN BALB C MICE INFECTED WITHEIMERIA-PAPILLATA DURING PRIMARY AND SECONDARY INFECTIONS/

BALB/c mice were infected with the intestinal intracellular parasite E imeria papillata to characterize lymphocyte responses and cytokine pro files throughout primary and secondary infections. Lymphocytes from th e mesenteric lymph node (MLN) and the gastrointestinal tract (GIT) of infected mice were phenotypically analyzed using flow cytometry and im munofluorescence microscopy, respectively. Lymphocytes isolated from t he MLN during primary infections of BALB/c mice with E. papillata do n ot proliferate, compared to day 0 uninfected controls, when stimulated in vitro with conconavalin A and express T(H)2-type cytokines (interl eukin [IL]-4 and IL-10) on day 3 PI followed by the release of T-H 1-t ype cytokines (IL-2 and interferon-gamma) during patency. In the small intestine, significantly more T cells and their subsets were observed during primary infection. During secondary infections, IL-2 was the o nly 1 of the 4 cytokines that was expressed earlier and at higher leve ls in the MLN when compared to primary infections. In the small intest ine, significantly more alpha beta(+) and CD8(-) T lymphocytes were ob served in mice during secondary infection. Oocyst antigens did not ind uce cellular proliferation at any rime point during primary or seconda ry infections. We conclude that primary oral infection of BALB/c mice with E. papillata is associated with localized immunosuppression that may be mediated, in part, by early T(H)2-type cytokines. Immunity to s econdary infection may be mediated by intestinal alpha beta(+)CD8(+) T lymphocytes through an IL-2-dependent mechanism.