The antibody response of vitamin A-deficient rats to pneumococcal polysaccharide is enhanced through coimmunization with lipopolysaccharide.

Although the antibody response of vitamin A-deficient rats immunized with pneumococcal polysaccharide (SSS-III) was barely detectable, coimmunization with SSS-III plus 2 or 20 micrograms of Pseudomonas aeruginosa lipopolysaccharide (LPS) resulted in an anti-SSS-III response that was equal to or greater than that of vitamin A-sufficient rats immunized only with SSS-III. Doses of 2 and 20 micrograms of LPS, but not 0.1 and 0.5 micrograms, produced significant adjuvanticity, and LPS functioned as an adjuvant when given concomitantly with SSS-III (day 0) or up to 3 days later. Thus, vitamin A deficiency per se does not preclude the anti-SSS-III response, and LPS or factors released in response to LPS, even after initiation of the response to SSS-III, may substantially enhance antibody production to this thymus-independent, type 2 antigen.