Determinants of helper T cell-dependent antibody production.

Multiple factors regulate the development and maintenance of humoral immune responses. The cytokines produced by helper T cells are major determinants of the magnitude and phenotype of antibody responses to protein antigens. Th2-derived cytokines are most effective at initiating primary B cell responses, whereas Th1 cells are effective helpers for B cells exposed to multivalent antigens and for previously activated B cells. In addition, different cytokines stimulate B cell switching to particular antibody isotypes. Cytokine production can be regulated in vivo by the conditions of antigen exposure, and by the nature of antigens. Tolerogenic antigens alter the phenotypes of antibody responses by preferentially inactivating selected subsets of helper T cells. Morphologic techniques provide potentially valuable approaches for studying T/B cell interactions and the nature and consequences of local cytokine production in situ, in lymphoid tissues.