CD32A CD32A is an activating subtype of CD32 that can be found on a variety of immune cells - notably, CD32A is found on
platelets,
neutrophils,
macrophages, and
dendritic cells (DCs). On platelets, it is known to aid in the internalization of IgG-
opsonized Escherichia coli, and it is more generally implicated in mediating bacterial-activated platelet responses. Thus, CD32B plays an important role in both antibody and
memory immune responses. The balance between CD32B and its activating counterparts is crucial to appropriate cell function. Having too little CD32B has been associated with dysregulated antibody function, as well as increased antibody-dependent inflammatory cell responses. Some individuals inheriting mutated, inactivate CD32B genes have a reduced risk of contracting malaria; this is attributed to an enhancement of FcR-dependent phagocytic functions. CD32B imbalance is also associated with autoimmunity. CD32B-deficient mice have been found to be more susceptible to immune-complex-mediated autoimmunity. Likewise,
systemic lupus erythematosus (SLE) in humans is associated with a decrease in CD32B on the surface of
memory B cells. A decrease on dendritic cells is often found in patients with
rheumatoid arthritis. The therapeutic usage of monoclonal antibodies against CD32B can be effective for inducing cytotoxicity against
B cell lymphoma cells. CD32B is also found on basophils, neutrophils, monocytes, and macrophages.
Non-immune system locations CD32B can be found on airway
smooth muscle cells, as well as
liver sinusoidal endothelial cells and
salivary gland epithelial cells.
CD32C CD32C is expressed in ~20% of the human population, and is not well-understood. It can be found on B cells and
natural killer (NK) cells. When expressed, CD32C plays an important role in the activation of
antibody-dependent cell cytotoxicity (ADCC). Animal studies have linked CD32C to augmentation of pathological inflammatory responses. == See also ==