Question

Endo/lysosomal proteases cleave proteins at different positions than the proteasome. Peptides generated by the vacuolar pathway can be expected to differ from those generated by the cytosolic pathway. Why might this be a problem for cytolytic T cell responses?

Answer 1

Vacoular pathway of anigen presentation: It processing and presentation of intracellular antigen by MHC-I molecules and recognised by cytotoxic T cell (CTL) expressed CD8 receptor. MHC-I molecule expressed on all the nucleated cells and protein degraded in small fragment by cytosolic proteases in the proteasome and experessed on nucleated cells with MHC-I molecules. MHCI shows the non specific immune responce.It kill the infected and damaged cell by inducing cytotoxicity. CD8

Cytosolic Pathway of antigen Presentation: It processing and presentation of extracellular antigen by MHC-II molecules and recognised by helper T cells expressing CD4 receptors. MHC II molecules only expressed on specialized antigen presenting cells like  dendritic cells, B cells or macrophages.MHC-II shows specific immune response than MHC-I . Proteins or antigens are degraded by lysosomes enzymes like acid-dependent hydrolases, glycosidases, proteases, lipases and forms oligopeptides of antigen.

Antigen presentation with MHC-II by cytosolic pathway in proffesional antigen presentation cells (dendritic cells, B cells or macrophages) are more specific and different from the antigen presentation with MHC-I by vacuolar pathway in nucleated cells.

Antigen processing and presentation is not a problem of cytotoxic T cell response. Cytotoxic T cells required additional costimulatory molecules and cytokines to activate  cytotoxic immune response. Cytotoxic T cell response regulated by number of factors.