BCL-6 GENE-PRODUCT, A 92-KD TO 98-KD NUCLEAR PHOSPHOPROTEIN, IS HIGHLY EXPRESSED IN GERMINAL CENTER B-CELLS AND THEIR NEOPLASTIC COUNTERPARTS

The BCL-6 gene is known to be located on chromosome 3q27, at the break point of the 3q27-associated translocations that occur frequently in h uman non-Hodgkin's lymphomas (NHLs), To identify the BCL-6 protein, tw o antibodies that recognized distinct domains of this protein were rai sed in rabbits. Immunoprecipitation and immunoblotting of lysates of B CL-6-expressing cells using both antibodies showed a broad 92- to 98-k D band. Dephosphorylation of BCL-6 protein reduced the size of this ba nd to 87 kD, suggesting that BCL-6 may be expressed in a phosphorylate d form. Immunostaining with both antibodies showed that BCL-6 protein was localized in the nuclei of most of the germinal center B cells and a small number of marginal zone B cells. Furthermore, BCL-6 protein w as expressed in follicular, Burkitt's, and diffuse large B-cell lympho mas. These results suggest that the BCL-6 protein, expressed in B cell s of the germinal centers which are important in the maturation of imm une responses, may play some physiological role(s) in the germinal cen ter b cells. (C) 1995 by The American Society of Hematology.