CD5-positive B cells in healthy elderly humans are a polyclonal B cell population

Abstract

B cell chronic lymphocytic leukemia (B‐CLL) is a disease of the elderly and is characterized by a malignant clone of CD5⁺ B cells. In old mice, clonal expansions of CD5⁺ B cells are a common feature, and these animals frequently develop B‐CLL. To investigate whether clonal expansion of CD5⁺ B cells also occurs in elderly humans, predisposing for the development of B‐CLL, we analyzed V_H gene rearrangements of CD5⁺ B cells from blood samples of four healthy, 65–82‐years‐old volunteers as markers of clonality. CD5⁺ and CD5^– B cells were obtained by cell sorting, CDRIII of rearranged V_H genes were amplified by polymerase chain reaction, and fragment length analysis was performed. All samples demonstrated a polyclonal pattern of V_H gene length distribution. In addition, V_H gene rearrangements were amplified and sequenced from sorted single cells of two of the donors. No clonally related CD5⁺ or CD5^– B cells were observed. Thus, development of dominant clones of CD5⁺ peripheral blood B cells is unlikely to be a common trait of elderly individuals.