Heterologous reactivity of in vitro cultured mouse cells with natural human serum antibodies.

Studies employing the cytotoxic and immunofluorescence tests revealed presence of natural human serum antibodies in the serum of various human donors, which reacted with normal and pathologic mouse cells cultivated in vitro. This reactivity was due to presence on the cell surface of heterologous HMAg antigen incorporated into the cell membrane from calf serum. Immunofluorescence studies demonstrated localization of this antigen on the cell surface. Absorption of human sera with calf serum or with lyophilized cow's milk abolished or markedly weakened the ability of these sera to react with cultured mouse cells.