A monoclonal antibody recognizing a human thymus leukemia‐like antigen associated with β2‐microglobulin

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Abstract
A monoclonal antibody, M241, was produced which binds to a human cell surface molecule with properties similar to the murine thymus leukemia (TL) antigen. This human TL‐like antigen was found on thymocytes and some T cell lines derived from patients with acute lymphocytic leukemia, but was not found on peripheral blood lymphocytes or B cell lines. The monoclonal antibody M241 was used to immuno‐precipitate a molecule from lysates of 125I surface‐labeled MOLT 4 cells which had two subunits, a 43‐kDa chain and a 12‐kDa chain. The small subunit was shown to be β2‐microglobulin (β2m) by immunoprecipitation with a monoclonal antibody, BBM.1, which recognizes human β2m. The TL‐like molecule recognized by M241 was shown to be serologically distinct from the HLA‐A, B, C molecules recognized by three monoclonal antibodies W6/32, PA2.6 and BB7.8, and distinct from another human thymocyte antigen, the 49 kDa HTA 1 molecule, recognized by the monoclonal antibody NA1 / 34. Following removal of the HLA‐A, B, C molecules, the HTA 1 molecules, and the M241‐defined TL‐like molecules from MOLT 4 lysates, additional β2m‐associated molecules were immunoprecipitated with BBM.1. These molecules contained a 45‐kDa subunit attached to β2m.