A Cryptosporidium parvum oocyst low molecular mass fraction evokes a CD4+ T-cell-dependent IFN-γ response in bovine peripheral blood mononuclear cell cultures

T-Cell antigens that induce the in-vitro interferon-gamma response during Cryptosporidium parvum infection of neonatal calves were identified. A total oocyst extract was separated into a high and a low M_r fraction by a microfiltration technique. Both the high and low M_r fractions evoked an in-vitro interferon-gamma response in naturally infected animals, although strong individual differences between the hosts were observed. Using a complement-mediated technique CD4⁺ T-cells or WC1⁺γδ T-cells were depleted, whereupon the remaining lymphocyte cultures were stimulated with the different antigen preparations. It was shown that the in-vitro interferon-gamma response of Cryptosporidium-infected calves is CD4⁺ T-cell-dependent.