Human colostral cytotoxicity. II. Relative defects in colostral leukocyte cytotoxicity and inhibition of peripheral blood leukocyte cytotoxicity by colostrum.

Colostral cells have been previously shown to mediate antibody-dependent cellular cytotoxicity (ADCC) to herpes to simplex virus-infected cells. A comparison of colostral cells to matched peripheral blood mononuclear cells has revealed significantly lower ADCC activity, higher antibody requirements, and slower kinetics of colostral cell ADCC against infected cells. Colostral cells failed to mediate natural killer cytotoxicity. Lymphocytes, monocyte macrophages, and polymorphonuclear leukocytes isolated from peripheral blood and incubated with colostrum from virus-immune or nonimmune women markedly inhibited ADCC. Inhibitory activity was found in lipid and aqueous fractions and was due to an effect on leukocytes, not target cells. A partial explanation was inhibition of expression of leukocyte Fc receptors, a prerequisite for ADCC, by acellular colostrum. These results raise questions concerning the potential antiviral activity of colostral cells in vitro.