MITOGENIC, IMMUNOGENIC AND TOLEROGENIC PROPERTIES OF DEXTRANS AND LEVANS - LACK OF CORRELATION ACCORDING TO DIFFERENCES OF MOLECULAR-STRUCTURE AND SIZE

Abstract

The mitogenicity of dextrans, levans and some of their depolymerized fractions was assayed in vitro using spleen cells from CBA mice and compared with their immunogenic and tolerogenic potency in vivo. Two branched dextrans (B1355 and B1299) induced a greater increase in DNA synthesis than linear dextran B512 which was only feebly mitogenic. The activity of B1355 was greater than that of B1299 and induced a level of stimulation similar to that of polyanions (dextran sulfate and polystyrene sulfonic acid). Dextrans B1355 and B1299 were relatively poor tolerogens for the .alpha.1-6 glucosyl epitope while the native linear dextran B512 was much more effective. Their immunogenicity for this specificity also decreased in the order B512, B1355, B1299. All depolymerized fractions of B512 induced only minimal mitogenic responses bearing no relevance to their immunogenic and tolerogenic potentials, which declined in parallel with decreasing MW to extinction at 2 .times. 104. Native levan, hydrolyzed fractions of it and perennial rye grass fructosans were all equally potent mitogens irrespective of their MW. The controlled hydrolysis of levan can, according to extent, abrogate its immunogenicity and tolerogenicity or immunogenicity alone. Discrimination between immunity and tolerance induced by T[thymus-derived] cell-independent antigens probably depends on the intensity of mitogenic stimulation to which they subject corresponding specific B [bone marrow-derived] cells.