Antibody repertoire development in fetal and neonatal piglets. XXII. λ rearrangement precedes κ rearrangement during B-cell lymphogenesis in swine

VDJ and VJ rearrangements, expression of RAG-1, Tdt and VpreB, and the presence of signal joint circles (SJC) were used to identify sites of B-cell lymphogenesis. VDJ, V?J? but not V?J? rearrangements or SJC were recovered from yolk sac (YS) at 20 similar to days of gestation (DG) along with strong expression of VpreB and RAG-1 but weak Tdt expression. V?J? rearrangements but not V?J? rearrangements were recovered from fetal liver at 3050 DG. SJC were pronounced in bone marrow at 95 DG where V?J? rearrangements were first recovered. The V?J? rearrangements recovered at 2050 DG used some of the same V? and J? segments seen in older fetuses and adult animals. Hence the textbook paradigm for the order of light-chain rearrangement does not apply to swine. Consistent with weak Tdt expression in early sites of lymphogenesis, N-region additions in VDJ rearrangements were more frequent at 95 DG. Junctional diversity in V?J? rearrangement was limited at all stages of development. There was little evidence for B-cell lymphogenesis in the ileal Peyer's patches. The widespread recovery of VpreB transcripts in whole, non-lymphoid tissue was unexpected as was its recovery from bone marrow and peripheral blood monocytes. Based on recovery of SJC, B-cell lymphogenesis continues for at least 5 similar to weeks postpartum.