Modulated selection of IGHV gene somatic hypermutation during systemic maturation of human plasma cells

Abstract

Systemic antigen-induced PCs are generated in inductive lymphoid tissues. Some of them are selected to travel through the circulation and finally, to home onto BM niches. BM PCs show prolonged survival and secrete high-affinity antibodies. In this study, human PCs were isolated from tonsil, blood, and BM, their IGHV3 and IGHV6 genes were sequenced, and their SHM were evaluated. The SHM analysis reveals the existence of a maturational gradient in these genes, as demonstrated by a progressive increase in the frequency of total and R mutations and total and NC aa changes following the direction: tonsil --> blood --> BM. The ratio of R to S mutations in the CDR1 and -2, but not in the FRs, increases from tonsil to blood and BM; this parameter reaches a maximum threshold when more than 10 mutations/sequence occur. Further analyses indicate that CDR1 and CDR2 SHM followed different strategies to provide appropriate amino acid changes, but both exhibited maximal resistance to incorporating drastic molecular alterations in the BM PCs. Finally, all of the findings are similar in IGHV3 and IGHV6 sequences, indicating that they reflect general rules imposed by in vivo antigen selection.

Differential expression of SLAMS and other modulatory molecules by human plasma cells during normal maturation

“…Moreover, several days after Ag booster immunization of normal volunteers, most circulating PCs secrete specific Abs, and are thought to contain the precursors of the BM PCs [19][20][21]. Furthermore, studies of the phenotype, IGVH gene somatic hypermutation and gene expression profiling support the view that human PCs obtained from tonsil and lymph node (as examples of inductive secondary lymphoid organs), from the blood drawn at the peak time of appearance of Ag-induced PCs (as a source of BM PC precursors) and from the BM (as the main final deposit organ for systemic humoral responses) exhibit a gradient of increasing maturation in the following direction: secondary lymphoid organs (tonsil and lymph nodes) → blood → BM [22][23][24][25][26].…”

“…PCs from human tonsil, PB and BM were defined by FACS analysis as CD19 + CD38 high , CD19 + CD27 high or CD19 + CD38 high and CD19 +/− CD38 high , respectively, as previously reported [21][22][23][24][25][26]. An example of the dot-plot analysis of these different PC populations is depicted in Fig.…”

Camelid Ig V genes reveal significant human homology not seen in therapeutic target genes, providing for a powerful therapeutic antibody platform

“…Strikingly, in humans, these "missing" families are known to be less frequently used than other IGHV families in VH/Vl pairing. 33,34 Surprisingly, macaque IGHV4 CDR1 and 2 contain one additional amino acid compared to humans (7-16 versus 8-17), which results in a different canonical structure (GenBank DQ437842). 31 Thus, despite the fact that macaques are more closely related to humans than camelids are, the canonical structures of the IGHV4 genes of the latter may be considered more human than those of the first (the latter not having these additional residues).…”

STAT-3 Activation by Differential Cytokines Is Critical for Human In Vivo–Generated Plasma Cell Survival and Ig Secretion

“…Moreover, 5-7 d after Ag booster immunization of healthy volunteers, most circulating PCs secrete specific Abs, show features of intermediate maturity, and are thought to contain the precursors of the BM PCs (14)(15)(16). Furthermore, comparative studies of the phenotype, BLIMP1 expression, gene expression profiling, and IGVH gene somatic hypermutation support the view that human PCs obtained from tonsil (To) and lymph node (as examples of early PCs from inductive SLOs), from the peripheral blood (PB) drawn at the peak time of appearance of Ag-induced PCs (as a source of transitional PCs), and from the BM (as terminally differentiated PCs) exhibit a gradient of increasing maturation in the following direction: SLOs→blood→BM (16)(17)(18)(19)(20). Besides this well-established migratory pathway, evidence in both humans and mice indicates that a non-negligible fraction of PCs survives in the SLOs, as well as in inflamed tissues, where they continue to produce Abs for prolonged periods (21)(22)(23)(24).…”