Macrophages: Phagocytosis, Antigen Presentation, and Activation of Immunity

Macrophages are phagocytes and one of the white blood cells discovered by Ilya I. Mechnikov in 1892. They engulf digest foreign substances like pathogens conduct antigen presentation, mature from haematopoietic stem bone marrow, moving into vessels become monocytes, differentiate macrophages tissue. have intracellular granules called lysosome accumulating digestive enzymes. Their life span is several months proliferates cell division. There three roles: First phagocytosis. incorporate work natural immunity. In inflammation, aggregate after neutrophils recruitment cellular phagosomes, fused with lysosomes degrade. Second role presentation. present fragment digested on surface MHC class II molecules release cytokines. Dendritic B also APCs expressing II. CD4+ T recognize antigens presented using TCR. Only well-matched helper via II-TCR interaction activated. The third activation Cytokines produced activate them inflammatory M1 wound-healing M2 macrophages.