Regulation of isotype immunoglobulin and interleukin production by adjuvants in vitro

Abstract

An in vitro system has been developed in which antibodies to fluorescein isothiocyanate (FITC)-labelled human gamma globulin (HGG) or dextran sulfate (DXS), are produced in the presence or absence of different adjuvants. The antibody response of in vitro cultures was measured by assaying the total Ig-secreting cells and FITC-specific plaque-forming cells (PFC). The presence of low levels of antigen and various cytokines were necessary for the production of isotypes other than IgM. Our results indicate that the regulation of isotype switching in vitro is dependent upon the non-specific stimuli-adjuvants, which probably activate different types of cells for cytokine production. The pre-activation of spleen cells, in our system, by antigen, seems to play a decisive role in the subclass of IgG produced. The adjuvant may still be able to influence the precommitted cell isotype to switch to another subclass but only in a "down-stream" direction i.e., IgG3----IgG1----IgG2b----IgG2a.