The conditions of the activation of immunological memory by means of flagellin and its conjugate with polyacrylic acid (PAA) have been studied. The flagellin-PAA conjugate has proved to be capable of inducing the appearance of memory cells when introduced in doses, considerably lower (0.01 and 0.001 micrograms) than those of native protein (0.1, 1 and 10 micrograms). At the same time no manifest differences in the reactivation of flagellin-induced and conjugate-induced memory cells by the antigen have been established. Immunization with protein, as well as with its conjugate, has been found to induce the formation of mainly anti-Hi : 1,2 IgG in secondary immune response.

The authors studied the activation effect in vitro of polyanionic mitogen-polyacrylic acid (PAA) on several types of mouse lymphocytes. The action of PAA was evaluated from an early effect on membrane (Na+, K+)- and Ca2+-ATPases. PAA was demonstrated to interact with the membrane of B cells from the spleen and immature T lymphocytes from the thymus, producing no effect on mature T cells from the spleen. The lack of the PAA effect on mature T lymphocytes was found to be linked with high density of negatively charged groups on the surface of these cells. Artificial lessening of the density of the negatively charged groups by the cleavage of the terminal N-acetylneuraminic residues with the aid neuraminidase leads to the change of mature T cells into PAA-sensitive ones.

A synthetic polysaccharide immunogen has been obtained by the conjugation of S. typhimurium nonimmune O-polysaccharide with a membrane-active adjuvant (the copolymer of acrylic acid and N-vinylpyrrolidone). The importance of the method used for the conjugation of O-polysaccharide with a synthetic carrier in enhancing its immunogenicity is shown.