A novel antigenic determinant of the T200 glycoprotein expressed exclusively by Jurkat cells.

: This report describes the production and characterization of monoclonal antibody specific for an antigenic determinant, designated Y1 antigen, present on Jurkat cells. Mo-Y1 specifically reacts with Jurkat cells, but not with other cell lines. Immunoprecipitation and subsequent immunochemical analysis demonstrate that Mo-Y1 defines an antigen with a molecular weight of 200,000 and a pI value of 5.3 to 5.6. Rabbit antibody against affinity-purified Y1 antigen was prepared. A sequential immunoprecipitation study confirmed that Po-Y1 reacted with the same antigen molecule recognized by Mo-Y1. Interestingly, Mo-Y1 reacted only with Jurkat cells, whereas Po-Y1 reacted with various hematopoietic cells including T cells, B cells, macrophages, and granulocytes. Po-Y1 precipitated a 200,000-dalton component from Jurkat cells and T cells. In contrast, Po-Y1 precipitated a 230,000-dalton component from B cells. These data led us to examine the relationship between T200, leukocyte-common antigen and Y1-defined antigen. Sequential immunoprecipitation analysis clearly indicated that T200 antibody and Y1 antibody recognized the same antigen molecule. Peptide mapping of T200- and Mo-Y1-defined antigen digested with V8 protease demonstrated that there were two common major peptide chains, but one peptide chain was missing in Jurkat cells that was present in T200 glycoprotein of other cells. It is possible that minor molecular modification of T200 glycoprotein occurred in the process of oncogenesis of T cells and that the altered epitope of T200 glycoprotein was recognized by Mo-Y1. The Y1 antigen can be classified as a tumor-specific antigen.