Abstract:B‐cell non‐Hodgkin's lymphomas (B‐NHL) and B‐cell areas of reactive lymphadenopathies were investigated immunohistochemically for expression of two distinct ICAM‐1 epitopes, Me14/D12 and P3‐58, and the LFA‐1 α and β chains. Partial or total loss of expression of one or both epitope(s) and/or chain(s) was evident in all B‐NHL in function of increasing Working Formulation (WF) malignancy grade, with most defects in the high‐grade tumors, namely the lowest detectability of the ICAM‐1 Me14/D12 and LFA‐1 α chain, the lowest co‐expression of ICAM‐1 epitopes and LFA‐1 chains, and the most frequent simultaneous loss. The ICAM‐1 and LFA‐1 profiles overlapped within the low‐ and intermediate‐grades, whereas striking differences between the high‐grade subtypes were detected. Specifically, Burkitt's and lymphoblastic tumors always lost both epitopes and both chains. Large cell, immunoblastic tumors occasionally did so, and also showed either uncoordinated expression or co‐expression of these constituents. It is suggested that expression defects of this type may help differentiate malignant from benign lymphoproliferations, and also be involved in the progression of B‐NHL, since most are observed in high‐grade tumors, whose ICAM‐1 and LFA‐1 profiles indicate that their subtypes are the expressio
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