POLYREACTIVE BINDING OF ANTIBODIES GENERATED BY POLYCLONAL CELL ACTIVATION .1. POLYREACTIVITY COULD BE CAUSED BY DIFFERENTIAL GLYCOSYLATIONOF IMMUNOGLOBULINS

The aim of this study was to gain knowledge of the pre-immune repertoi re with reactivity directed to the carbohydrate antigen dextran B512, (Dx). Polyclonal activation of spleen cells in mice has been estimated to be a method of revealing the available repertoire. Hybridoma cell lines derived from lipopolysaccharide-(LPS)stimulated C57BL/6 spleen c ells were screened for reactivity with Dx and with the non-related pro tein bovine serum albumin (BSA). Despite the lack of structural simila rity between Dx and BSA we observed that nearly all of the Dx positive monoclonal antibodies (MoAbs) cross-reacted with BSA. The Dx and BSA crossreactive MoAbs were also found to bind to several foreign-and aut o-antigens, and therefore we concluded that these MoAbs fulfilled the criteria of polyreactivity. The Dx and BSA cross-reactive antibodies w ere produced in an apparently random fashion as judged by the use of k appa and lambda light chains and the use of V-H J558 subfamily genes. There are two possible explanations for this type of polyreactivity: ( 1) LPS induces a randomly generated polyreactive and a randomly genera ted specific immunoglobulin (Ig) repertoire; (2) polyreactivity can be the result of post-translational modifications. Since immunoglobulins are glycoproteins we considered the possibility that post-translation al modifications such as glycosylation could be responsible for the ge neration of the polyreactive pool. Dextran-specific and Dx/BSA cross-r eactive MoAbs showed different degrees of sensitivity to inhibition of glycosylation performed by treatment with tunicamycin (Tm), an inhibi tor of the formation of N-glycosidic linkages. Other polyreactive, con nective and specific MoAbs were also tested. The authors found that Tm treatment had a more profound effect in reducing the binding capacity of the polyreactive antibodies (Abs), suggesting that the polyreactiv e Abs may be more dependent than the specific Abs on the carbohydrate content of the molecule for binding to the antigens. The authors propo se that lymphocytes may use differential glycosylation as a means to g enerate polyreactive or monospecific Abs.