Effect of lymphokine treatment on the invasion of cultured animal cells by Eimeria tenella.

Cultured animal cells were pretreated with crude cytokines from E. tenella-immune chicken spleen cells to determine whether the invasion of these cells by sporozoites of E. tenella could be affected. Treatment of both primary chicken kidney (CK) cells and the established Madin-Darby bovine kidney cell line (MDBK) with the crude avian cytokines caused an increased invasion of the cultures by the parasite. Apparently, the cytokine treatment of the cells increased the susceptibility or sensitivity of the host cells to invasion as evidenced by the increased number of the total cells infected and not by an increased number of sporozoites/infected cell. This increased host cell susceptibility to infection induced by the crude avian cytokines was: (a) dose-dependent; (b) non-host species specific, since it affected both avian and bovine cells; and (c) non-parasite species specific, since cytokines from E. tenella and E. maxima-immune chicken spleen cells and E. nieschulzi-immune rat spleen cells also increased the invasion of the CK and MDBK cells by E. tenella. However, treatment of MDBK cells with lymphokines induced from purified E. tenella-immune splenic T lymphocytes inhibited the invasion of the cells by E.tenella sporozoites. Therefore, the increased susceptibility of the host cells is caused by a B cell-or macrophage-mediated factor. Although the identity of the factor or factor(s) is unknown, this in vitro-lymphokine-E.tenella system should provide an excellent model to aid in the identification of cellular binding sites and/or penetration mechanisms for cellular invasion by the Eimeria.