Effect of bacterial lipopolysaccharide on the in vitro secondary antibody response in mice. I. Description of the suppressive capacity of lipopolysaccharide.

Bacterial lipopolysaccharide (LPS) suppressed the in vitro secondary antibody response in mice to the protein antigens human gamma globulin (HGG) and turkey gamma globulin (TGG). This is the first report of LPS inhibiting a secondary antibody response. Consistent suppression was dependent on the time of LPS addition; LPS added at culture initiation was less effective than LPS added 12 to 48 hr later. The mitogenic moiety of LPS was the inhibitory principle, as shown by the lack of suppression of spleen cells from C3H/HeJ mice, and the inability of the polysaccharide component, but not the lipid component of LPS, to suppress A/J spleen cells. The mechanism of suppression by LPS was not due to large numbers of B cells proliferating in response to LPS, since removal of B cells not bearing specificity for the priming antigen did not reduce suppression by LPS. However, the possibility exists that LPS may act through B cells specific for the priming antigen.