Antigen presentation in the immune response to infectious diseases

T lymphocytes mediate immune defenses against infectious diseases. The majo r histocompatibility complex class I and class IT antigen-processing pathwa ys play an essential role in the activation of pathogen-specific T lymphocy tes bq presenting peptide fragments derived from pathogen-encoded proteins, The past 5 years have seen remarkable advances in our understanding of bot h of these antigen-processing pathways. Many new proteins that are critical to T-cell-mediated defenses against infections pathogens have been identif ied and characterized. Although the direct effects of aging on antigen proc essing and presentation are relatively unexplored. it is likely that immuno senescence affects and is affected by the antigen-processing pathways.