Distorted antibody repertoire developed in the absence of pre-B cell receptor formation

作者：Sun Lin; Kono Naoko; Shimizu Takeyuki; Toh Hiroyuki; Xue Hanbing; Numata Osamu; Ato Manabu; Itamura Shigeyuki; Ohnishi Kazuo^*

来源：Biochemical and Biophysical Research Communications, 2018, 495(1): 1411-1417.

DOI：10.1016/j.bbrc.2017.11.171

• Surrogate light chain
• Antibody repertoire
• Next generation sequencing

The pre-B cell receptor (pre-BCR), consisting of the mu heavy chain (mu EC) and the surrogate light chain (SLC, Vpre-B and lambda 5), plays important roles during B cell development. The formation of the pre-BCR, which enables the nascent immunoglobulin HC to associate with the SLC, is considered a prerequisite for B cell development. However, a significant number of peripheral mature (leaky) B cells exist in SLC-deficient mice. These leaky B cells develop in the absence of pre-BCR and do not undergo the pre-BCR checkpoint. The antibody repertoires of leaky B cells thus reflect the absence of pre-BCR function. To investigate how the absence of the pre-BCR is circumvented by these leaky-B cells and examine the effect of the pre-BCR checkpoint on the antibody system, we analyzed the antibody repertoires of lambda 5-deficient (lambda 5(-/-)) mice using next-generation sequencing. In lambda 5(-/-) mice, spleen B cells displayed different patterns of VDJ-usage, relative to those in wild-type (WT) mice. Moreover, leaky B cells were neither derived from unusual B2 cells, characterized by particular LC gene rearrangements in the absence of pre-BCR signaling, nor from B1 cells, originating from different B cell progenitors. Analysis of the CDR-H3 amino acid sequences of mu-chain repertoires revealed that certain bone marrow B cells with particular CDR-H3 profiles undergo clonal expansion in lambda 5(-/-) mice. Part of these CDR-H3s contain arginine(s) in the middle of the CDR-H3 loop in lambda 5(-/-) mice, whereas few arginine(s) exist in this middle loop in WT CDR-H3s in the absence of clonal expansion. This CDR-H3 feature in lambda 5(-/-) mice presumably reflects the role of the pre-BCR in autoantibody regulation, since arginine(s) are often found in the antigen-binding site of auto antibodies. Here, we present a unique viewpoint on the role of pre-BCR, by assessing the whole antibody repertoire formed in SLC-deficient mice.

• 出版日期2018-1-1