REQUIREMENT FOR INVARIANT CHAIN IN B-CELL MATURATION AND FUNCTION

Previously the role of invariant chain (ii) had been described only as a chaperone that facilitates folding and transport of major histocomp atability complex class II molecules; here it is shown that Ii is requ ired for B cell development. B cells from mice lacking Ii were found t o have a low response to T-independent type II antigen and could not p roliferate after the mice were injected with antigen. Study of cell su rface markers revealed a developmental arrest that prevented immature virgin B cells from becoming mature B cells in the periphery. This blo ck was independent of major histocompatability complex class II expres sion and was an intrinsic feature of B cells that correlated with the amount of Ii. Thus, Ii participates by an unknown mechanism in B cell maturation.