Cytotoxicity in Immune Defenses Against Intracellular Parasites
Although CTL were discovered in the course of trying to understand the immunological basis for allograft rejection, it was not until the 1970s that the true significance of CTL began to be understood: the detection and elimination of cells compromised by intracellular parasites, and possibly by oncological transformation. Viable intracellular parasites produce parasitespecific proteins during their sojourn in the host cell. Fragments of these peptides are displayed at the host cell surface in association with MHC class I molecules, which leads to their elimination by host CTL. This provides a critical adjunct to the role of antibodies, which are only able to effect the elimination of nonself antigens from the extracellular milieu. By far the heaviest intracellular parasite burden consists of the wide range of viruses that find vertebrate cells a good (and necessary) place to reproduce, but CTL responses are also provoked by intracellular bacteria and eukaryotic parasites with obligate host intracellular stages in their life cycles.
KeywordsIntracellular Parasite Infected Target Cell Nonclassical Class Killer Lymphocyte Eukaryotic Parasite
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