Bovine IgG and human immune responses: Con A-induced mitogenesis of human mononuclear cells is suppressed by bovine IgG.

Abstract

Cow's milk contains 0.6-0.9 mg/ml of IgG. Under certain circumstances humans might potentially absorb significant amounts of bovine IgG and/or large fragments of bovine IgG from their diets. Normal human peripheral blood mononuclear cells were cultured with bovine milk IgG and various mitogens to begin to investigate whether bovine IgG might influence human immunologic responses. Elsewhere we have shown that bovine milk IgG at concentrations of 300 micrograms/ml completely suppressed synthesis of IgG, IgA, and IgM (96-98% suppression) in pokeweed (PWM)-stimulated cultures. Suppression was dose dependent from 40 to 300 micrograms/ml. Milk-derived bovine IgG heated at 63 degrees C during 30 min was more potent in suppression than unheated IgG. IgG from goat's milk also suppressed Ig synthesis. Bovine serum IgG and other xenogeneic serum immunoglobulins, even when heat-aggregated, had little effect on Ig synthesis. Preincubation of MNCs with bovine milk IgG and PWM for 1 day followed by washing and incubation with PWM for 14 days resulted in suppression of antibody secretion. In this study, Con A-stimulated cultures were pulsed after 3 or 4 days with 3H-thymidine for 4 h, and mitogenic responses were measured. Bovine IgG at concentrations as low as 300 micrograms/ml significantly suppressed the mitogenic response of human mononuclear cells. These studies suggest that ingested milk immunoglobulins may have the potential to modulate immune responses in humans.