Lymphocyte mediation of lipopolysaccharide-stimulated macrophage metabolism

LPS activation of murine macrophage metabolism and arginase production may be mediated by products of B lymphocytes. Splenic nonadherent cells, containing both B and T lymphocytes, splenic T cells, and thymocytes all stimulated macrophage glucose metabolism in co-culture. Supernatants derived from preculturing each of these cells in the absence of serum or other exogenous stimulant were also active in enhancing macrophage glucose utilization. When lipopolysaccharides were used to stimulate the lymphocyte populations, only the B lymphocyte containing NASC and purified B cells exhibited increased stimulatory activity. Thus, it appears that LPS does not directly activate T cells to produce macrophage-activating factors. The converse does not appear to be true, however, because LPS-stimulated macrophages enabled thymocytes to exhibit an enhanced ability to stimulate further macrophage glucose utilization. The active supernatant from NASC was heat resistant and remains to be chemically defined. These experiments clearly demonstrate that LPS-induced macrophage activation may be mediated by the products of lymphocytes, and that products derived from nonactivated lymphocytes are capable of stimulating macrophage metabolism and arginase production.