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No correlation between CD73 expression and ecto‐5‘‐nucleotidase activity on blood mononuclear cells in vitro
Author(s) -
CHRISTENSEN LISA DALH
Publication year - 1996
Publication title -
apmis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.909
H-Index - 88
eISSN - 1600-0463
pISSN - 0903-4641
DOI - 10.1111/j.1699-0463.1996.tb00697.x
Subject(s) - 5' nucleotidase , microbiology and biotechnology , peripheral blood mononuclear cell , in vitro , biochemistry , monoclonal antibody , gene isoform , enzyme , chemistry , biology , antibody , immunology , gene
Monoclonal antibodies against ecto‐5′‐nucleotidase (ecto‐5′‐NT) have been clustered to CD73. The aim of the present study was to elucidate whether specific ecto‐5′‐NT activity on blood mononuclear cells (BMC) was correlated with CD73 expression measured by flow cytometry. During culture of CD73‐negative lymphocytes the percentage of cells with ecto‐5′‐NT activity increased without there being a comparable increase in CD73 expression. After 2 days' culture, 9% (3–16, median and range given) demonstrated ecto‐5′‐NT activity, whereas CD73‐positive cells comprised only 1.6% (0.0–3.0). These results show the existence of lymphocytes with ecto‐5′‐NT activity but without expression of CD73. The ecto‐5′‐NT activity increased significantly (p<0.02) during culture of unseparated BMC, whereas the number of anti‐CD73 binding sites did not change. As a consequence, the number of anti‐CD73 binding sites per U ecto‐5′‐NT activity decreased during culture. Exposure to interleukin‐4 or prostaglandin E 2 changed the enzymatic activity but not the number of anti‐CD73 binding sites. Treatment of BMC with phosphatidylinositol‐specific phospholipase‐C released 57% (51%–75%) of the ecto‐5′‐NT activity into the supernatants, without a detectable decrease in CD73 expression. The fact that ecto‐5′‐NT was removed from the supernatant after precipitation with anti‐CD73 showed that the released ecto‐5′‐NT activity was due to enzymatic activity of CD73 molecules. The results of this study indicate that CD73 exists on BMC in isoforms with distinct capacities to bind mouse monoclonal anti‐CD73.