Dietary protein influences the responsiveness of splenocytes to Con A in growing mice

Abstract

The effects of dietary proteins containing different levels of sulfur amino acid on the responsiveness of splenocytes to concanavalin A(Con A) were examined. The Con A-induced DNA synthesis of splenocytes in mice fed a purified egg protein(PEP) diet was significantly higher than those in mice fed a soy protein isolate(SPI) or casein diet. Reduced glutathione(GSH) and 2-mercaptoethanol(2-ME) markedly stimulated Con A-induced DNA synthesis in vitro, and the stimulatory effects of 2-ME were more marked in SPI and casein diet groups compared to the PEP diet group. In contrast, L-buthionine-( S,R)-sulfoximine(BSO) markedly inhibited Con A-induced DNA synthesis in splenocytes. The degree of inhibition was greater in the order SPI, casein and PEP diet groups. The Con A-induced IL-2 secretion from splenocytes in the SPI diet group was significantly lower than those in casein and PEP diet groups when BSO was added to the medium. IL-2 secretion from splenocytes in the SPI diet group was significantly increased by L-methionine supplementation in the diet. These results suggest that the sulfur amino acids content in the dietary protein may play a key role in the regulation of lymphocyte responsiveness to Con A in growing mice.