Role of the CD45 tyrosine phosphatase in signal transduction in the immune system.

CD45, a family of hematopoietic cell specific surface antigens, is the best characterized protein tyrosine phosphatase described to date. Considerable evidence from a number of laboratories suggests that surface expression of this molecule is required for normal signaling events to occur in T lymphocytes, B lymphocytes, and natural killer cells. In this paper, data supporting this contention are reviewed and a model proposing how CD45 may exert its regulatory function on signal transduction via the T cell antigen receptor is presented.