EndoU is a novel regulator of AICD during peripheral B cell selection

Poe, Jonathan C.; Kountikov, Evgueni I.; Lykken, Jacquelyn M.; Natarajan, Abirami; Marchuk, Douglas A.; Tedder, Thomas F.

Whether reduced B cell AICD led to the depletion of sHEL auto-Ag in EndoU / Ig Tg sHEL mice with age was examined. Blood B220 + cells isolated from Ig Tg and high-responder development and c-Myc expression after BCR ligation, increased spleen B cell numbers and surface IgM a expression, and reduced CD5 and HSA expression (Fig. 6, E and F) . In fact, high-responder mice were comparable to Ig Tg and EndoU / Ig Tg littermates lacking sHEL auto-Ag, except that surface IgM a levels were modestly decreased. In contrast, augmentedresponder EndoU / Ig Tg sHEL mice remained phenotypically similar to Ig Tg sHEL mice. Some B cells in augmentedresponder mice exhibited surface IgM a levels comparable to high-responder and Ig Tg B cells (Fig. 6 F, small peak) , but otherwise their B cells had reduced IgM a expression, modest blast development and c-Myc expression after BCR ligation, Fig. 1 C. The isotype control shown is the same for the HSA and IgD groups because a common fluorochrome of the same isotype was used for detection. Results are representative of three mice of each genotype assessed in independent experiments producing similar results.