Monoclonal antibodies to antigen on activated human B-cells and assay therefor, protein antigenic determinant therefor and method of making same

This patent describes a monoclonal antibody recognizing an antigenic determinant on activated human B-cells. The antigenic determinant is characterized in that it is a protein distinct from B-LAST-1 and BB-1 and is a protein on the surface of activated B-cells having an apparent molecular weight of approximately 75,000 daltons under reducing conditions and 67,000 daltons under non-reducing conditions. The antibody is a protein of the IgM isotype and is reactive with less than 1% of unstimulated human B-cells, with less than 6% of stimulated or resting T-cells and monocytes, and unreactive with neoplasms of non-B-cell origin, or neoplasms of B-cell origin corresponding to stages of differentiation other than the mid-stage of B-cell differentiation