Mitogenic activities of synthetic Escherichia coli lipid A and a synthetic partial structure (tripalmitoyl pentapeptide) of E. coli lipoprotein.

Synthetic Escherichia coli lipid A and synthetic S-[2,3-bis-(palmitoyloxy)propyl]-N-palmitoylpentapeptide (tripalmitoyl pentapeptide [TPP]), representing the mitogenically active principles of bacterial lipopolysaccharide (LPS) and lipoprotein, respectively, were compared for their mitogenic activities on splenocytes of LPS responder (BALB/c) and LPS-low-responder (C3H/HeJ) mice. Whereas lipid A was active only in LPS-responder mice, TPP resulted in mitogenic activation of B lymphocytes from both LPS-responder and LPS-low-responder mice. When the mitogens were added simultaneously, mainly additive effects of both activators were observed. The data suggest that two different B-lymphocyte populations are responding to these two mitogens.