Immunoregulating effects of peptidoglycan monomer linked with zinc in adult mice

Since it is well known that both zinc ions and bacterial immunostimulants influence the function of the immune system, in the present study we investigated the immunomodulating activity of a new analog of peptidoglycan monomer (PGM), in which the basic molecule was linked to zinc (PGM-Zn). Its effects in BALB/c mice, aged 10-12 months, were compared with the effects of equimolar doses of PGM and ZnCl2. The treatment lasted 26 days (one i.p. injection every fifth day). The results showed that PGM-Zn may markedly enhance antibody production to sheep red blood cells, as well as spontaneous and concanavalin A (ConA)-induced blastogenesis. The generation of plaque-forming cells in individual mouse was positively correlated with the expression of class II antigens in the liver and negatively correlated with the total quantity of hepatic proteins. PGM-Zn also induced the appearance of peritoneal macrophages, which in cocultures with syngeneic splenocytes were less able to enhance the spontaneous, and particularly the ConA-induced blastic transformation. The enhancing activities of PGM-Zn were in some respects more closely correlated with the action of PGM, whereas the induction of suppressive macrophages resembled more the activity of ZnCl2. The data emphasize that PGM-Zn may both stimulate and inhibit immunoregulative pathways by mechanisms which are not identical to those of PGM or ZnCl2.