Autoreactive B-1 B cells: Constraints on natural autoantibody B cell antigen receptors

B-1 B-cells constitute a distinctive population of cells that are enriched for self-reactive B cell receptors (BCRs). These BCRs are encoded by a restricted set of heavy and light chains, including heavy chains that lack nontemplated nucleotide additions at the V–D and D–J joining regions. One prototype natural autoantibody produced by B-1 B cells binds to a cryptic determinant exposed on senescent red blood cells that includes the phosphatidylcholine (PtC) moiety. The VH11Vκ9 BCR, which accounts for a large fraction of the anti-PtC specificity, is underrepresented in other B-cell populations, including newly formed B cells in bone marrow, and the transitional B cells, follicular B cells, and marginal zone B cells in spleen. Previous work has shown that VH11 heavy chains pair ineffectively with surrogate light chain (SLC) and so do not promote development in bone marrow, but instead allow fetal liver maturation because of a fetal preference for weaker pre-BCR signaling. Such inefficient SLC pairing constitutes one constraint on the maturation of B cells containing VH11 rearrangements that biases their generation to fetal development. Here, we examine another possible bottleneck to the B1 cell repertoire: light chain pairing with VH11 heavy chain, finding very significant preferences.