Reactivity of Leu 1 and T101 monoclonal antibodies with B cell lymphomas (correlations with other immunological markers).

The reactivity of Leu 1/T101 monoclonal antibodies (MoAb) was studied in a series of 69 lymphomas with B cell differentiation and was correlated with other cell markers. A three step immunoperoxidase technique on frozen sections was used to test a panel of 20 MoAb: anti-human Ig (heavy and light chains), To 15 (Pan B cells), Leu 1, T101, Leu 4, Leu 3a, Leu 5, OKT 8, OKT 6, Leu 7, anti-CALLA (IOT 5), Leu 10, anti-HLA-DR, OKM 1 and anti-dendritic reticulum cells (R 4/23). T101/Leu 1 antigen was detected in 24 cases: CLL (11 of 11), diffuse centrocytic lymphomas (four of 11), follicular lymphomas (none of 12), follicular and diffuse lymphomas (seven of 10) and one unclassified low grade lymphoma. This antigen was observed in only one high grade malignant lymphoma. In follicular lymphomas, two results deserve attention: (1) T101+ lymphomas showed most frequently IgM+, IgD+ surface Ig. Inversely, T101 unreactive lymphomas displayed IgM+, IgD+ phenotype. (2) Tp67 antigen (T101, Leu 1) and CALLA (GP 100) were found to be mutually exclusive in these lymphomas. These results suggest that follicular lymphomas could be derived from two distinct germinal center cell populations: IgM+ Ig'D-, Calla+, Leu 1-/T101- and IgM+, IgD+, CALLA-, Leu+/T101+.