CD43 and CD5 antibodies define four normal and neoplastic B‐cell subsets: A three‐color flow cytometric study

CD43 antibodies are best known for identifying normal and neoplastic T cells and a subset of neoplastic B cells in paraffin sections. The frequency of nonneoplastic CD43 + B cells in different reactive settings, the proportion of B‐cell neoplasms with small CD43+ populations, and the relationship of CD43+ B cells to CD5+ B cells are less well established. CD43 and CD5 expression on normal and neoplastic CD19 + B cells was therefore studied in 138 specimens using three‐color flow cytometric analysis. CD43 and CD5 defined four normal B‐cell subsets (CD43 + CD5 +, CD43 + CD5−, CD43−CD5+, and CD43−CD5−). A significantly greater proportion of CD43+ B cells was found in cord blood and putative HIV + blood samples than in normal control bloods. B‐cell neoplasms derived from each of these four B‐cell subsets were identified, with CD43 +/CD5+ and CD43‐/CD5‐ neoplasms being most common. The predominant B‐cell population coexpressed CD43 alone in 2/39 neoplasms and CD5 alone in four. A minority of cases showed heterogeneous CD43 expression. The B cells in two of three posttransplant lymphoproliferative disorders coexpressed CD43. B cells showed weaker CD43 staining than did T‐cells (relative fluorescence 0.38 ± 0.29). These findings support the concept that CD43 expression by neoplastic B cells is not an aberrant finding. CD43 expression on normal and neoplastic B cells is independent of CD5 expression even though CD43 and CD5 are frequently coexpressed. CD43 expression by B cells sometimes might be underestimated in paraffin sections because it is much weaker than on T cells. Although large discrete populations of CD43+ B cells were only identified in B‐cell neoplasms and posttransplant lymphoproliferative disorders, increased proportions of CD43+ B cells were present in some benign settings. © 1995 Wiley‐Liss, Inc.