PEPTIDE-MEDIATED IMMUNOREGULATION

Quantitative and qualitative characteristics of the signals received b y a T cell determine whether receptor ligation results in cell activat ion, cell death, or the induction of antigen-specific non-responsivene ss. Environmental factors such as the nature of costimulation, antigen -presenting cell type, peptide structure and cytokine levels also infl uence the differentiation of CD4+ helper T cells into functionally dis tinct subsets, which now appear pivotal in many immune-mediated disord ers, including autoimmunity and allergy. Selective manipulation of the immune response, such as the functional inactivation or deviation of the cytokine secretion patterns of specific T cells, may be an effecti ve strategy for immunotherapy.