Lysosomes are thought to play an impoant role in which of the following processes?

Class I and Class II MHC-restricted presentation of antigen by other cell types to T cells occurs by different mechanisms and serves different purposes. Class II presentation is used for exogenous, extracellular protein antigens. The following steps are involved in this process: internalization of the protein by endocytosis into endosomes, processing within lysosomes of protein into immunogenic peptides, fusion with vesicles containing class II MHC molecules, binding of the peptide to the class II MHC molecules, and then fusion of the vesicle to the cell membrane so that the antigen-class II complex is available for binding to T cells on the cell surface. Class I MHC-restricted antigen presentation is used for endogenous antigens, and the proteolytic process is thought to occur in the endoplasmic reticulum. Ig gene rearrangement and T cell receptor rearrangement do not involve proteolysis or lysosomes.