engleski

Detection of BCL-6 gene expression in human naive and memory B cells with real-time PCR

B cells are undergoing intensive proliferation after encountering their specific antigen and their cooperating T cells in germinal centres (GC), structures in secondary lymphoid tissues. Consequently, GC B cells differentiate into either memory B cells or plasma cells. BCL-6 is a "gene signature" of GC B cells which blocks terminal differentiation of these cells into plasma cells. The aim of the study was to investigate whether naive and memory B cells possess equal capacity to participate in GC formation. Highly purified human tonsilar naive and memory B cells were stimulated via BCR and/or CD40, surrogate signals for B cells engaged in T-dependent signalling, necessary for GC formation. Semiquantitative multiplex real-time PCR was used to compare changes in BCL-6 mRNA levels between these cells following stimulations. The expression BCL-6 failed to increase under any of the stimulation conditions. Memory B cells down-regulated BCL-6 mRNA in response to BCR and/or CD40 signals, indicating that this subset might have reduced the capacity for GC entry as compared with naive counterparts. Immunohistochemistry analysis at the protein level showed that freshly isolated memory B cells were positive and naive B cells were negative for BCL-6 protein. Furthermore, our results suggested that in vitro conditions did not appear adequate to generate complete GC phenotype in either naive or memory population. It is necessary to identify additional signals in vitro for generating full GC B cell phenotype in vivo.

naive and memory B cells; human; BCL-6 mRNA; real-time PCR

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