Heterogeneity in cytokine profiles of Babesia bovis-specific bovine CD4+ T cells clones activated in vitro

Abstract

The central role of T cells in the immune response against hemoprotozoan parasites, both as helper cells for T cell-dependent antibody production and as effector cells acting on intracellular parasites through the elaboration of cytokines, has prompted an investigation of the bovine cellular immune response against Babesia bovis antigens. CD4+ T helper (Th) cell clones generated from four B. bovis-immune cattle by in vitro stimulation with a soluble or membrane-associated merozoite antigen were characterized for reactivity against various forms of antigen and against different geographical isolates of B. bovis and B. bigemina and analyzed for cytokine production following mitogenic stimulation with concanavalin A. Biological assays to measure interleukin-2 (IL-2), IL-4, gamma interferon (IFN-gamma), and tumor necrosis factor alpha or tumor necrosis factor beta and Northern (RNA) blot analysis to verify the expression of IL-2, IL-4, IFN-gamma, and tumor necrosis factor alpha revealed differential production of cytokines by the Th cell clones. The majority of clones expressed the Th0 pattern of cytokines: IFN-gamma, IL-4, and IL-2. One clone expressed the Th1 profile (IFN-gamma and IL-2 but not IL-4), whereas none of the clones expressed the Th2 profile. All of the Th cell clones examined expressed the low-molecular-weight isoform of the leukocyte common antigen associated with a memory cell phenotype (CD45RO), and all expressed the lymph node homing receptor (L-selectin). These results extend our previous finding of differential cytokine expression by B. bovis-specific Th cell clones and confirm the identity of the specific cytokines produced, showing that a Th0 response is preferentially induced in a panel of 20 CD4+ T cell clones obtained from immune cattle.