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Antigen presentation is a vital immune process that is essential for T cell immune response triggering. Because T cells recognize only fragmented antigens displayed on cell surfaces , antigen processing must occur before the antigen fragment can be recognized by a T-cell receptor .
HLA-A projected away from the cell surface and presenting a peptide sequence. The peptide-MHC complex presents a surface that looks like an altered self to the TCR. [11] The surface consisting of two α helices from the MHC and a bound peptide sequence is projected away from the host cell to the T cells, whose TCRs are projected away from the T cells towards the host cells.
As with B cells, each type of T cell recognizes a different antigen. Killer T cells are activated when their T-cell receptor binds to this specific antigen in a complex with the MHC Class I receptor of another cell. Recognition of this MHC:antigen complex is aided by a co-receptor on the T cell, called CD8. The T cell then travels throughout ...
It is in this way, the MHC class I-dependent pathway of antigen presentation, that the virus infected cells signal T-cells that abnormal proteins are being produced as a result of infection. The fate of the virus-infected cell is almost always induction of apoptosis through cell-mediated immunity, reducing the risk of infecting neighboring ...
It is considered to be a stage of antigen presentation pathways. This process involves two distinct pathways for processing of antigens from an organism's own (self) proteins or intracellular pathogens (e.g. viruses ), or from phagocytosed pathogens (e.g. bacteria ); subsequent presentation of these antigens on class I or class II major ...
Antigen presentation stimulates immature T cells to become either mature "cytotoxic" CD8+ cells or mature "helper" CD4+ cells. An antigen-presenting cell (APC) or accessory cell is a cell that displays an antigen bound by major histocompatibility complex (MHC) proteins on its surface; this process is known as antigen presentation.
Once the exogenous antigen peptide is loaded onto the MHC class I molecule, the complex is exported to the cell surface for antigen cross presentation. There is also evidence that suggest that cross-presentation requires a separate pathway in a proportion of CD8(+) dendritic cells that are able to cross-present.
After the processed antigen (peptide) is complexed to the MHC molecule, they both migrate together to the cell membrane, where they are exhibited (elaborated) as a complex that can be recognized by the CD 4+ (T helper cell) – a type of white blood cell. [note 7] [20] This is known as antigen presentation.