Antigen Presentation
Adaptive immunity relies on the capacity of immune cells to distinguish between the body's own cells and unwanted invaders. The host's cells express "self" antigens. These antigens are different from those on the surface of bacteria ("non-self" antigens) or on the surface of virally infected host cells (“missing-self”). The adaptive response is triggered by recognizing non-self and missing-self antigens.
With the exception of non-nucleated cells (including erythrocytes), all cells are capable of presenting antigen and of activating the adaptive response. Some cells are specially equipped to present antigen, and to prime naive T cells. Dendritic cells and B-cells (and to a lesser extent macrophages) are equipped with special immunostimulatory receptors that allow for enhanced activation of T cells, and are termed professional antigen presenting cells (APC).
Several T cells subgroups can be activated by professional APCs, and each type of T cell is specially equipped to deal with each unique toxin or bacterial and viral pathogen. The type of T cell activated, and the type of response generated depends, in part, on the context in which the APC first encountered the antigen.
Read more about this topic: Adaptive Immune System
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