PECAM-1^−/− mice show a transient developmental block in B-cell maturation in the periphery.

The developmental block in B-cell maturation was defined by decreased percentage numbers of mature IgD⁺-expressing B cells in the spleen. Representative scatter plots of splenic lymphocytes from PECAM-1^+/+ (n = 26) and PECAM-1^−/−(n = 26) mice. Dissociated splenocytes were dual stained to identify (A) immature B cells (B220⁺/IgM⁺) and (B) mature B cells (B220⁺/IgD⁺). All dotplots contain data for this representative experiment, and oval boxes indicate low and high IgD expression levels.