Alterations in the antibody response to bovine serum albumin by capsular polysaccharide of Klebsiella pneumoniae.

Immunologic paralysis was induced in mice by administration of large amounts of the capsular polysaccharide of Klebsiella pneumoniae (CPS-K). When a paralyzing dose of CPS-K was injected into mice 3 to 30 days before immunization with bovine serum albumin (BSA)-Freund's adjuvant complex, the immune response of mice to BSA was markedly depressed. Conversely, when a paralyzing dose of CPS-K was injected simultaneously with or 3 days after immunization with BSA-Freund's adjuvant complex, the immune response to BSA was enhanced. Paralyzing doses of CPS-K had a marked adjuvant effect on antibody formation to BSA, which is a weak immunogen when administered without any adjuvant. The adjuvant effect of CPS-K was most marked when it was administered simultaneously with BSA. In mice paralyzed with CPS-K serum γ globulin, splenic weight and phagocytic activity of the reticuloendothelial system increased markedly.