In order to investigate functional variation of antigenic epitopes and expression patterns of hematopoietic cells and biochemical characteristics, we produced murine monoclonal antibodies, anti-YG 14 and anti-YG 15, against human thymocytes. We
found
that these monoclonal antibodies recognized same surface molecule which has been confirmed by immunoprecipitation analysis. This antigen was expressed in peripheral monocytes, subset of T cells, platelets, and epidermis of skin, but not expressed
in
granulocytes and peripheral B cells. It was approximately 24KDa protein in molecular weight and expressed as monomer. Its expression patterns and biochemical characteristics were similar to those of leukocyte differntiation antigen, CD9. With
blocking
test, we found out that YG14, YG15 monoclonal antibodies recognized different epitopes of same molecule, using flow cytometry. With the results of colony forming assay, it is very intriguing to see that YG15 monoclonal antibody showed increased
colony
forming activity but the YG14 monoclonal antibody did not. These results strongly suggest that engagement of different epitopes of same molecule can show different functional activity.
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