B-CELL DEVELOPMENT UNDER THE CONDITION OF ALLELIC INCLUSION

Mice whose IgH alleles are engineered to encode two distinct antibody heavy (H) chains generate a normal-sized B cell compartment in which m ost cells stably express the two heavy chains. This demonstrates that ''toxicity'' of bi-allelic H chain expression and cell-autonomous mech anisms of silencing in-frame IgH gene rearrangements do not significan tly contribute to allelic exclusion at the IgH locus. Notwithstanding, the stability of the various engineered IgH loci during B cell develo pment in the bone marrow differed substantially from each other.