Mutations in the tyrosine phosphatase CD45 gene in a child with severe combined immunodeficiency disease

The hematopoietic-specific transmembrane protein tyrosine phosphatase CD45 functions to regulate Src kinases required for T- and B-cell antigen recept or signal transduction(1,2). So far, there have been no reports to our know ledge of a human deficiency in a tyrosine-specific phosphatase. Here, we id entified a male patient with a deficiency in CD45 due to a large deletion a t one allele and a point mutation at the other. The point mutation resulted in the alteration of intervening sequence 13 donor splice site. The patien t presented at 2 months of age with severe combined immunodeficiency diseas e. The population of peripheral blood T lymphocytes was greatly diminished and unresponsive to mitogen stimulation. Despite normal B-lymphocyte number s, serum immunoglobulin levels decreased with age. Thus, CD45 deficiency in humans results in T- and B-lymphocyte dysfunction.