CD11b is involved in various adhesive interactions of monocytes, macrophages and granulocytes as well as in mediating the uptake of complement-coated particles. CD11b is identical with CR-3, the receptor for the iC3b fragment of the third complement component. Genetic variations in CD11b have been associated with susceptibility to systemic lupus erythematosus type 6 (SLEB6). SLEB6 is a chronic, inflammatory and often febrile multisystemic disorder of connective tissue. It affects principally the skin, joints, kidneys and serosal membranes.
The CD45 antigen (Receptor-type tyrosine-protein phosphatase C, PTPRC) is a protein tyrosine-protein phosphatase required for T-cell activation through the antigen receptor. CD45 acts as a positive regulator of T-cell coactivation upon binding to DPP4. Defects in CD45 are a cause of severe combined immunodefiency autosomal recessive T-cell negative/B-cell-positive/NK-cell-positive (T-B+NK+ SCID). Genetic variations in CD45 are involved in multiple sclerosis susceptibility.