ECTO-5'-NUCLEOTIDASE ACTIVITY IS NOT REQUIRED FOR T-CELL ACTIVATION THROUGH CD73

It had previously been shown that CD73 (ecto-5'-nucleotidase) expresse d on 30% of normal human peripheral T-lymphocytes can mediate costimul atory signals in T cell activation, To check for a possible contributi on of the catalytic property of CD73 to this function transfected cell lines were created, Using site-directed mutagenesis on human CD73 cDN A the codons of His92 and His194 were exchanged for alanine codons. Wi ld type and mutant cDNAs were cloned into an expression vector and sta bly expressed in the T cell line Jurkat, Surface expression as quantit ated by immunofluorescence with anti CD73 mAbs was comparable in wild type and mutant transfectant clones, whereas in contrast to the wild t ype both His to Ala mutants completely lacked enzymatic activity, The Jurkat transfectants were stimulated with a combination of soluble ant i-CD73 mAb and PMA and their response was quantitated by IL-2 producti on, The responses of different clones of wild type and mutant transfec tants varied within a wide range; however, the ranges of wild type and mutants overlap, It is concluded that in order to transmit costimulat ory signals CD73 does not require its catalytic activity. (C) 1995 Aca demic Press, Inc.