Retroviral and Lentiviral Vectors for the Induction of Immunological Tolerance

Figure 4

Antigen presentation and T cell responses. Activation of T cell responses by antigen presenting dendritic cells is shown in the figure. On the left, a DC is presenting antigenic peptides associated to MHC I (sphere containing “I”) or MHC II (sphere containing “II”) molecules. CD8 or CD4 T cells recognise these peptide-MHC molecules together with additional receptor-ligand interactions (costimulation, represented by bars connecting the DC with each T cell). These interactions accompanied by the presence of a wide range of cytokines will drive T cell proliferation (right). CD8 T cells will then differentiate into cytotoxic T lymphocytes, and CD4 T cells into helper T cells which will collaborate in raising antibody responses. T helper differentiation can lead to either immunological tolerance or different types of immune responses, such as a “Th1-” type (mainly cellular immunity) or a “Th2-” type (mainly humoral immunity).