CD45 (LEUKOCYTE COMMON ANTIGEN) EXPRESSION IN T-LYMPHOCYTE AND B-LYMPHOCYTE SUBSETS

CD45 is the dominant tyrosine phosphatase in haematopoietic cells and can modulate the effects of many other signaling molecules by dephosph orylation. The extracellular portion of CD45 has considerable variabil ity 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 gly cosylation can distinguish between cell populations that differ in mat uration and function. These reagents can be used in the immunophenotyp ing of hematopoietic malignancies as well as in immunodeficiencies and autoimmune diseases. Several studies have shown that different anti C D45 reagents have different activating or inhibiting effects in vitro on a variety of T and B cell activation events. There are some indicat ions that anti CD45 reagents can also selectively modify lymphocyte fu nction in vivo. Such applications could potentially allow for the sele ctive upregulation and down regulation of lymphocyte functions in a va riety of immunologically mediated diseases.