Translocations involving the BCL-6 gene are common in the diffuse large cell subtype of non-Hodgkin's lymphoma. Invariably, the BCL-6 coding region is intact, but its 5′ untranslated region is replaced with sequences from the translocation partner. The present study shows that BCL-6 expression is regulated in lymphocytes during mitogenic stimulation. Resting B and T lymphocytes contain high levels of BCL-6 mRNA. Stimulation of mouse B cells with anti-IgM or IgD antibodies, bacterial lipopolysaccharide, phorbol 12-myristate 13-acetate plus ionomycin, or CD40 ligand led to a five-fold to 35-fold decrease in BCL-6 mRNA levels. Similar downregulation of BCL-6 mRNA was seen in human B cells stimulated with Staphylococcus aureus plus interleukin-2 or anti-IgM antibodies and in human T lymphocytes stimulated with phytohemagglutinin. BCL-6 mRNA levels began to decrease 8 to 16 hours after stimulation, before cells entered S phase. Although polyclonal activation of B cells in vitro invariably decreased BCL-6 MRNA expression, activated B cells from human germinal centers expressed BCL-6 mRNA at levels comparable to the levels in resting B cells. Despite these similar mRNA levels, BCL-6 protein expression was threefold to 34-fold higher in germinal center B cells than in resting B cells, suggesting that BCL-6 protein levels are controlled by translational or posttranslational mechanisms. These observations suggest that the germinal center reaction provides unique activation signals to B cells that allow for continued, high-level BCL-6 expression.
ARTICLES| June 15, 1996
BCL-6 expression during B-cell activation
Blood (1996) 87 (12): 5257-5268.
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D Allman, A Jain, A Dent, RR Maile, T Selvaggi, MR Kehry, LM Staudt; BCL-6 expression during B-cell activation. Blood 1996; 87 (12): 5257–5268. doi: https://doi.org/10.1182/blood.V87.12.5257.bloodjournal87125257
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