Cross-reaction of 791T/36 monoclonal antibody with immunological activated human peripheral blood mononuclear cells.

Monoclonal antibody 791T/36, directed against surface antigen on the human osteosarcoma cell line (791T), and cross-reacting with surface antigen p72 expressed on activated (PHA, MLR) human peripheral blood mononuclear cells (PBM), was used in analysis of p72 antigen in vitro. Using FACS-IV system and fluorescence microscope, it was shown that expression of p72 antigen on PBM cells is dependent on phytohaemagglutinin (PHA) stimulation, and alloantigens in mixed lymphocyte reaction (MLR). The increase of p72 expression is always connected with lymphocytes proliferation activity (FACS-IV analysis and 3H-Thymidine incorporation assay). The expression of p72 is not significantly dependent on cell size, and stage of the cell in the cell cycle. A suggestion, that p72 is a one of so-called "proliferation antigens" is discussed. Present study emphasizes a problem of cross-reactivity in the context of possible errors in diagnosis and therapy, when a monoclonal antibody cross-reacts with cells other than intendent target cells.