Analysis of costimulatory molecule expression on antigen-specific T and B cells during the induction of adjuvant-induced Th1 and Th2 type responses.

Previous studies show that the generation of maximal T cell responses requires B cell antigen presentation and the differential expression of costimulatory molecules by B cells may affect polarization of naïve T cells to Th1 or Th2 phenotypes. We have therefore characterized the expression of activation and costimulatory molecules on antigen-specific T and B cells following immunisation with Alum or Alum/LPS to induce Th2 or Th1 responses in vivo. While antigen-specific B cells show similar levels of activation with respect to MHCII upregulation following Th1 or Th2 induction, they differentially express costimulatory molecules. Although ICOS-B7RP-1 interactions were originally implicated in Th2 generation, surprisingly this receptor-ligand pair was only upregulated on antigen-specific T and B cells following Th1 induction. In conclusion, these studies indicate that during the generation of antigen-specific Th1 or Th2 responses, adjuvants induce differential costimulation in antigen-specific B cells that may subsequently influence T cell polarization.