Reactivity of the monoclonal antibody RFB1 in chronic B‐cell leukaemias

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Abstract
The monoclonal antibody RFB1, which reacts with early haemopoietic precursors in human bone marrow and peripheral T‐lymphocytes, but not with pre‐B cells and mature peripheral blood and marrow B lymphocytes, was tested in blood from 60 patients with chronic B cell leukaemias. All 37 cases of B chronic lymphocytic leukaemia (B‐CLL) and 9 of hairy cell leukaemia (HCL) were positive. The antibody showed particularly strong reaction in HCL. On the other hand, RFB1 did not react with peripheral blood and B lymphocytes from 9 patients with non‐Hodgkin lymphoma (NHL) in leukaemic phase and was negative or weakly expressed in 5 with prolymphocytic leukaemia (B‐PLL). These findings may be significant for investigations on the cell origin of B‐CLL and HCL. The reactivity of RFB1 was different from that of two anti‐T1 monoclonal antibodies. The combined use of these reagents gave distinct patterns in B‐CLL (RFB1+, T1+), HCL (RFB1++, T1‐) and NHL and B‐PLL (RFB1‐/±, T1‐/+), suggesting they may be of value in the differential diagnosis of these B‐lymphoproliferative disorders.