Читать книгу Immunology - Richard Coico - Страница 95

The most important function of complement in host defense is considered to be the generation of fragments with opsonic activity that deposit on the surface of pathogens (see Figure 4.6A). C3b and C4b are the major opsonins generated, but iC3b, a fragment of C3b that does not activate complement, also has opsonic activity. Bacteria coated by opsonins are rapidly taken up and destroyed by phagocytic cells such as macrophages and neutrophils. These cells express the receptors CR1, CR3, and CR4, which have broad specificities for complement pathway‐generated opsonins and for other complement components. Complement receptor of the immunoglobulin family (CRIg) is expressed on tissue‐resident macrophages, including those found in liver (Kupffer cells). It interacts with C3b and iC3b. CR1 is also a regulator of complement activation, as described earlier (see Figure 4.5).