ANTIGEN PRESENTATION TO TH1 AND TH2 CELLS

CD4(+) T lymphocytes play an essential role in the induction and regul ation of the immune response. The two subpopulations, Th1 and Th2, are also able to activate various immune functions via their capacity to synthesize various cytokine patterns. CD4(+) T lymphocytes are activat ed by interaction of the T receptor with a bimolecular complex compose d of a peptide derived from processing of the antigen and a major hist ocompatibility complex class II molecule. Only a limited number of cel ls are able to activate CD4(+) T lymphocytes. Monocytes/macrophages, d entritic cells and B lymphocytes are usually responsible for presentat ion of the antigen to CD4(+) T lymphocytes. The capacity of phagocytos is, B7 molecules expression and the nature of the cytokine produced di ffer between these various cell types. This may play an essential role in the preferential activation of one or other of the Th1 and Th2 sub populations. Particulate antigens were prepared by covalent binding to synthetic microspheres in order to orient CD4(+) T lymphocyte respons es towards Th1 polarisation. These particles were presented to T lymph ocytes by macrophages, but not by B lymphocytes. When injected in the presence of poly (I)-(C) or IL-12, these particulate antigens preferen tially activated a Th1 type response.