IMMUNE-RESPONSE AGAINST 2 EPITOPES ON SAME THYMUS-INDEPENDENT POLYSACCHARIDE CARRIER .2. ENHANCED ANTIHAPTEN RESPONSES BY INJECTION OF UNCONJUGATED CARRIER

Abstract

Dextran B512 preparations of various MW induced polyclonal antibody synthesis in vivo. The efficiency of activation decreased with the MW. Dextran also markedly enhanced the anti-hapten (fluorescein-isothiocyanate-FITC) response after injection of immunogenic doses of FITC dextran. The adjuvant activity decreased with the MW of unconjugated dextran. The concentration of dextran which was necessary for adjuvanticity induced complete tolerance to the .alpha.1-6 epitope. Native dextran acted as an effective adjuvant and was capable of inducing polyclonal activation even in mouse strains that fail to produce antibodies to the .alpha. 1-6 epitope of dextran B512. The adjuvant property of dextran did not require T [thymus-derived] cells. Lipopolysaccharide from Escherichia coli did not act as an adjuvant for the anti-FITC response after injection of immunogenic doses of FITC-dextran. Since unconjugated dextran markedly enhanced the specific anti-FITC response after injection of FITC-dextran, the polyclonal activating property of dextran is capable of delivering an activation signal for the induction of specific immune responses to haptens coupled to dextran. Since LPS was not an adjuvant for the immune response to FITC-dextran, although LPS is a potent adjuvant for heterologous thymus-dependent red cell antigens, LPS and dextran probably act as polyclonal B [bone marrow-derived] cell activators on different B cell subpopulations.