Search

Abstract. Involvement of dendritic cells (DC) into switching of immune response to T-independent type 2 antigens (TI2 antigens) is poorly studied. The present study addressed some interactions between DCs and TI2-type antigens, i.e., with Streptococcus pneumoniae polysaccharide type 3 (S3), and polyvinylpyrrolidone (PVP, mw. of 360 kDa), as well as a role of antigen-loaded DCs for triggering the immune response. Shortterm treatment of DCs with TI-2 antigens induced their activation manifesting as an increase in numbers of CD80- and CD86-positive cells under the cell culture conditions. DCs loaded with TI-2 antigens were then mixed with normal murine splenocytes and cultured in complete RPMI 1640 medium for 4 days. The numbers of antibody- and immunoglobulin-forming cells (AFCs and IFCs, respectively) were determined by ELISPOT assay. Supplementation with TI2-treated DCs induced a 2.0 to 2.7-fold increase in specific immune response. Antigen-induced polyclonal response was enhanced by 40%. These data suggest a direct interaction between DCs and TI-2 antigens, and their presentation to murine splenocytes, thus leading to both specific and polyclonal B cell activation. B-1 cells are shown to play a main role in such response. Separation of loaded DC and splenocytes by semi-permeable membranes caused inhibition of this immune response.

Abstract. Interactions between B1, B2 and bone marrow dendritic cells (DCs) of CBA mice were investigated in the course of immune response to T-independent antigen type 2 (TI 2 Ag) in model system. Splenocytes of Xid-mice CBA/N were used as “fillers”. It was shown that DCs augmented viability of B1 and B2 lymphocytes. Functional activity of the B1 and B2 lymphocytes was determined by ELISPOT method, as relative numbers of antibody- and immunoglobulin-forming cells (AFCs and IFCs, respectively) detectable after four days in culture. An increased immune response to TI 2 Ag in presence of DCs was observed mainly for B2 subpopulation, containing MZ-B lymphocytes as well. Specific effect of DC upon B2 cell subpopulation was confirmed by detection of direct in vitro interactions of DCs with T and B lymphocytes. DCs cultivated with B2 and T lymphocytes, used as fillers, decreased the numbers of AFCs and IFCs, irrespectively of absence or presence of TI-2 Ags. A decrease in AFC and IFC numbers in the cultures with B1 cells was evident in presence of the Ags only. It was shown that the inhibitory effect of DCs depended on their contact interactions. Separate cultures of B1 and B2 cells with DC under transwell conditions resulted into occurence of AFC and IFC in amounts similar to those generated in vitro without DCs.