PECAM1 and glomerulonephritis: PECAM-1 deficiency also causes hyperactivation of B cells to BCR cross-linking, with PECAM-1-deficient mice exhibiting reduced B2 cell numbers in the periphery and increased peritoneal B1 cells, as well autoantibody production, culminating in glomerulonephritis (216) – all features shared by Lyn-/- mice.