Major histocompatibility complex costimulatory molecule expression

PMN have been found at many inflammatory and autoimmune disease sites. Since they are phagocytic cells, it has been proposed that they may have the capacity to develop into antigen-presenting cells (APC) and trigger an adaptive immune response [94]. The expression of major histocompatibility complex (MHC) and costimulatory receptors has been attributed exclusively to APC, which traditionally do not include PMN. However, recent evidence suggests that PMN can express both MHC class 1 and 11 as well as costimulatory molecules under certain circumstances [95-98]. 

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