Restoration of depressed antibody responses of leukemic splenocytes treated with LPS-induced factors.

Lipopolysaccharide and a nontoxic derivative, PS, from Serratia marcescens were studied in terms of their effects on normal and Friend leukemia virus depressed splenocytes. These materials caused a marked increase in the number of antibody producing cells by both groups of splenocytes. MDP, a synthetic analogue of myobacterial cell walls, produced a similar adjuvant response by normal and leukemic splenocytes. Combinations of PS or LPS and BCG or MDP resulted in synergistic immunostimulatory responses. A soluble factor associated with these materials appeared to mediate the response, since cell-free supernatants from LPS stimulated splenocytes or serum from LPS treated mice resulted in similar immunostimulation.