The propensity to apoptosis of centrocytes and centroblasts correlates with elevated levels of intracellular myc protein.

In this study, we investigated the c-myc expression by tonsillar germinal center (GC) B cells using reverse transcriptase-polymerase chain reaction, flow cytometry, Western blot and in situ immunohistochemical methods. The results obtained demonstrate elevated levels of c-myc mRNA and of Myc protein in GC B cells compared to those of the other resting or activated tonsillar B cells. Separation of GC B cells into centroblasts and centrocytes revealed that, while differing in their cell cycle status, surface marker expression and morphology, the two cell types had the same propensity to apoptosis and elevated Myc protein expression, thus reinforcing the notion of a close correlation between these two events. Based upon these observations and other considerations it is proposed that elevation of Myc proteins confers to GC B cells a particular propensity to apoptosis, while the subsequent decision between progression into the cell cycle or programmed cell death is dictated by other signals that are delivered in the GC and perhaps operate at the level of other proto-oncogenes.