CD45 (leucocyte common antigen) expression in T and B lymphocyte subsets.
CD45 is the dominant tyrosine phosphatase in haematopoietic cells and can modulate the effects of many other signaling molecules by dephosphorylation. The extracellular portion of CD45 has considerable variability due to differential splicing and glycosylation. This may allow for interactions with a variety of ligands expressed on interacting cells or on the same cell surface. Monoclonal anti CD45 antibodies that are reactive with epitopes that result from differential splicing and glycosylation can distinguish between cell populations that differ in maturation and function. These reagents can be used in the immunophenotyping of hematopoietic malignancies as well as in immunodeficiencies and autoimmune diseases. Several studies have shown that different anti CD45 reagents have different activating or inhibiting effects in vitro on a variety of T and B cell activation events. There are some indications that anti CD45 reagents can also selectively modify lymphocyte function in vivo. Such applications could potentially allow for the selective upregulation and down regulation of lymphocyte functions in a variety of immunologically mediated diseases.