CD11b Expression and the Innate Immune System

Why CD11b is important in Immunity: (Ref: Novus Biologicals)

CD11b is an integrin - Integrins are receptors that mediate attachment between a cell and the tissues surrounding it.
CD11b is expressed on the surface of many leukocytes including monocytes, neutrophils, natural killer cells, granulocytes and macrophages, as well as on 8% of spleen cells and 44% of bone marrow cells.
Functionally, CD11b regulates leukocyte adhesion and migration to mediate the inflammatory response.
CD11b antibody studies have shown the protein to be directly involved in cellular adhesion, although migration can only take place in the presence of the CD18 subunit.
As well as playing a role in various adhesion reactions, CD11b is a receptor for complement C3bi, mediating complement-coated particle uptake. Research using CD11b antibodies has identified CD11b as a receptor for fibrinogen gamma chain peptides, factor X and ICAM1, with possible roles in cell-mediated cytotoxicity, chemotaxis and phagocytosis.
Until recently, mouse CD11b expression had only been reported in detail for neutrophils and monocytes. In 2005, Kawai et al. undertook a CD11b antibody study to clarify CD11b function in B cells. Flow cytometry was used to isolate peripheral CD19+ B cells, and their migratory function was verified via transwell assays. Using CD11b antibody preparations, the contribution of Cd11b to migratory ability was then determined. It was seen that naïve B cells had little migratory capability and were CD11b negative. Memory B cells, however, had a high degree of motility and expressed CD11b. Given these findings, the authors suggested that CD11b plays an essential role in memory cell migration.