Antigen Processing and Presentation by MHC Class I, II, and Nonclassical Molecules

A successful vaccine delivers the pathogenic agent or a component thereof in an immunogenic form, without eliciting the disease pathology, which enables an effective immune response with long-lasting protection. The effectiveness and protection offered by vaccination requires the successful activation of the acquired immune response elicited primarily by thymus (T) and bone marrow (B) derived lymphocytes. Activation of T lymphocytes requires engagement of their specialized T cell receptors with cell surface molecules encoded by the major histocompatibility complex (MHC). These are categorized into MHC class I, class II, and nonclassical molecules. T lymphocytes control the magnitude of their own response and enable a successful B cell response. Therefore, the mechanism of peptide generation (antigen processing) and loading onto MHC molecules (antigen presentation) are pivotal to a successful immune response and effective vaccination, especially when considering the generation of recombinant vaccines.