Studies on Immunological Paralysis IX. THE IMMUNOGENICITY AND TOLEROGENICITY OF LEVAN (POLYFRUCTOSE) IN MICE.

The immunological response to native levan (a fructose homopolymer with molecular weight 2 × 10⁷) has been studied in (DBA/1 × CBA-T6T6)F₁ mice by passive hemagglutination and plaque-forming cell (PFC) assays. It resembles type-specific pneumococcal polysaccharide (SSS) in eliciting a prolonged humoral antibody response over a wide dose range (0.0001-100 µg) and in inducing longlasting 'high zone' tolerance with a single injection (1 mg or more). Other similarities include an exclusively IgM response, independence of synergy with thymusderived lymphocytes and absence of immunological memory. On the other hand, parallelism between serum hemagglutinin and PFC levels following all doses of antigen implies that higher immunizing doses of levan, unlike SSS, do not engage in peripheral neutralization of antibody. It was concluded from studying the fate of ¹⁴C-labelled levan that this was attributable to more rapid elimination from the circulation and subsequent slow metabolism of this polysaccharide. Levan also differs from SSS in inducing tolerance directly, without a detectable prior immune phase. [ABSTRACT FROM AUTHOR]