Germline variable region gene segment derivation of human monoclonal anti-Rh(D) antibodies. Evidence for affinity maturation by somatic hypermutation and repertoire shift.

Abstract

To date, there has been no systematic study of the process of affinity maturation of human antibodies. We therefore sequenced the variable region genes (V genes) of 14 human monoclonal antibodies specific for the erythrocyte Rh(D) alloantigen and determined the germline gene segments of origin and extent of somatic hypermutation. These data were correlated with determinations of antibody affinity. The four IgM antibodies (low affinity) appear to be derived from two germline heavy chain variable region gene segments and one or two germline light chain variable region gene segments and were not extensively mutated. The 10 IgG antibodies (higher affinity) appear to be derived from somatic hypermutation of these V gene segments and by use of new V gene segments or V gene segment combinations (repertoire shift). Affinity generally increased with increasing somatic hypermutation; on average, there were 8.

SNPs of hemocyanin C‐terminal fragment in shrimp Litopenaeus vannamei

“…2). Taken into consideration of our previous findings that hemocyanin C-terminal fragment displayed homology with Ig variable regions, it would be interesting to know if these SNPs in HcSC region were derived from random somatic mutations, a process which is used during affinity maturation of Ig [25]. In support of this hypothesis, Zhang et al reported that somatic hypermutation was one of the mechanisms present in FREPs of snails to obtain molecular diversity [21].…”

Redemption of autoantibodies on anergic B cells by variable-region glycosylation and mutation away from self-reactivity

“…Four of the identified antibodies were RhD-specific agglutinating IgM antibodies used in blood typing, and indeed the IgM response to foreign RhD is dominated by IGHV4-34*01 antibodies (16,20). Three of the anti-RhD IgM antibodies retain the AVY sequence and are known to retain self-reactivity measured by agglutination of I/i antigen-bearing erythrocytes (20).…”

“…To extend earlier evidence that IGHV4-34+ IgD+ IgM low anergic B cells are recruited into physiological germinal center (GC) responses against foreign antigens (15), we performed a Blastn search of the National Center for Biotechnology Information (NCBI) nonredundant nucleotide database using the IGHV4-34*01 sequence. The search revealed 14 human antibodies with a hypermutated IGHV4-34*01 sequence that had been elicited in normal individuals by repeated immunization either with allogeneic RhD+ erythrocytes (16), rotavirus (17), vaccinia virus (18), or tetanus toxoid (19) (Fig. 1A).…”

“…Glycosylated BCRs may also be recognized by lectins on follicular dendritic cells or macrophages in the germinal center to deliver a survival advantage (26). A need for some preimmune antibodies to mutate away from self-reactivity provides an alternative explanation for the phenomenon of repertoire shift during the maturation of antibody responses, when certain antibody specificities that ultimately dominate responses to haptens (52)(53)(54)(55)(56)(57) or RhD alloantigens (16,20) or bind conserved neutralizing epitopes of viruses (58)(59)(60)(61)(62) are minimally represented in the primary wave of plasma cells but gradually emerge after repetitive stimulation by foreign antigen. Inherited defects that prevent hypermutation away from self-reactivity by antimicrobial antibodies may explain the surprising prevalence of autoantibodies in human AICDA deficiency, where GCs are formed but hypermutation is crippled (63).…”

Identification, Isolation, and Culture of HLA-A2-Specific B Lymphocytes Using MHC Class I Tetramers

“…The availability of HLA-specific B cell lines permits the analysis of their Ig H and L chain genes in terms of V family usage. Such analyses have been reported for specific B cells in other antigenic systems (9), but for alloimmunity these studies have been done on established hybridomas (21,22). The anti-HLA-A2 repertoire has been studied by phage display (23); however, this technology is unable to distinguish correct pairing of H and L chain genes within single B cells.…”