Innate Immunity

What is the Cellular Role of the CD11 Protein?

The CD11 protein is actually a heterodimer complex that consists of CD11b and CD18. CD11 is involved in numerous adhesion-related associations between cells such as monocytes, macrophages, natural killer (NK) cells, and granulocytes. CD11 also regulates the uptake of complement-coated particles within cells. It has also gained usage as a microglial marker for tissues derived from the nervous system.

CD16 is a lymphocyte Fc gamma type III low-affinity receptor for IgG and is represented by two similar genes, CD16A (Fc gamma RIII A) and CD16B (Fc gamma RIIIB). CD16A exists as a heterooligomeric polypeptide-anchored form in macrophages and NK cells. CD16B exists as a monomeric glycosylphosphatidylinositol (GPI)-anchored form in neutrophils. CD16 binds IgG in the form of immune complexes or free antibody. It exhibits preferential binding to IgG1 and IgG3 isotypes, with minimal binding of IgG2 and IgG4.

The CD (Cluster of Differentiation) nomenclature was established in 1982 at the First International Workshop on Human Leukocyte Differentiation Antigens. It was intended for the classification of leukocytes according to the specific epitopes found at the cell surface, and at this inaugural meeting 139 monoclonal antibodies were evaluated.