| Background: | CD11b is implicated in various adhesive interactions of monocytes, macrophages and granulocytes as well as in mediating the uptake of complement coated particles. It is identical to CR3, the receptor for the iC3b fragment of the third complement component. It probably recognizes the RGD peptide in C3b. CD11b is also a receptor for fibrinogen, factor X and ICAM1. It recognizes P1 and P2 peptides of fibrinogen gamma chain. The Mac1 CD11b antigen is present on macrophages, granulocytes, natural killer cells, blood monocytes. CD11b is expressed on 8% spleen cells, 44% bone marrow cells and less than 1% of thymocytes and is commonly used as a microglial marker in nervous tissue. |