Immunization with immune complex alters the repertoire of antigen‐reactive B cells in the germinal centers

Abstract

The differentiation of memory B cells in germinal centers (GC) is selectively enhanced upon administration of antigen-antibody complexes. To characterize the repertoire of this response, we examined the rearranged immunoglobulin heavy chain variable (V(H)) genes from mouse splenic GC after a single immunization with either antigen, nitrophenyl (NP) hapten coupled to keyhole limpet hemocyanin, or with a preformed complex of antigen with a monoclonal anti-NP antibody of gamma1 isotype. Among antigen-immunized mice, NP-reactive GC B cell populations in the antigen-induced GC consisted mostly of cells expressing the canonical V186.2 gene which contained, on average, 0.8 point mutations/V(H) gene by day 8 after immunization. These results are indicative of the beginning of somatic hypermutation and consistent with previously published analyses of NP antigen-driven GC. In contrast, the NP-specific B cells in GC that were elicited by administration of immune complex represented a heterogeneous cell population expressing nine different germ-line segments of the V186.2/V3 (J558) gene family, i.e. V23, V24.8, C1H4, V3, CH10, V165.1, V102, V671.5 and V186.2. Moreover, the average frequency of mutations in these genes was 1.7, reaching up to 4 mutations/V(H) in some GC. Administration of the antigen NP in complex with specific antibody apparently alters the process of interclonal competition in the GC and results in loss of dominance by V186.2+ cells and nearly stochastic representation of diverse clonotypes. These results suggest an important feedback regulation of the B cell repertoire by antibody and indicate a role for immune complexes in the activation of somatic hypermutation.

Further Characterization of Immunomodulation by a Monoclonal Antibody againstStreptococcus mutansAntigen P1

“…Although factors which dictate whether an antibody complexed with an antigen will change an immune response are not fully understood, several mechanisms have been suggested, and they include increased uptake of antigen via Fc receptors on antigen-presenting cells (30), masking of dominant epitopes by antibody (2, 31), exposure of cryptic epitopes induced by antibody binding (49,53), enhanced germinal center formation and induction of somatic hypermutation (26,41), and/or alterations in proteolysis and antigen processing (30,32,49). Monoclonal antibody 6-11A against S. mutans adhesin P1 influences the specificity and isotype distribution of the serum IgG response in mice immunized with whole cells by gastric intubation (8).…”

Antibody-Mediated Immunomodulation: a Strategy To Improve Host Responses against Microbial Antigens

“…Immunomodulation by antibody can be Fc-dependent or independent and can include increased uptake of antigen via FcR on antigen-presenting cells (66,73), differential engagement of stimulatory versus inhibitory FcR (40,51,53,104,126), FcR-dependent enhancement of MHC class I-restricted cross-presentation (41,98,119), alterations in proteolysis and antigen processing (6,72,73,103,121), a shift in presentation of class II-restricted T-cell determinants (4,5,70), changes in cytokine expression by antigen-presenting cells and/or T cells (3,4,11,12), masking of dominant epitopes by antibody (6,9,10,14,72,121), exposure of cryptic epitopes induced by antibody binding (61,103,121), enhanced germinal center formation and generation of strong recall responses (53,59,60,62,64,91,108), changes in usage of germline-encoded V H genes (85,109), and induction of somatic hypermutation (85,108,109).…”

“…Immunization with IC has been reported to accelerate the development of B memory cells, the formation of GC, and the maturation of antibody affinity compared with immunization by antigen alone (62). In studies designed to analyze how immunization with IC can alter the repertoire of antigen-reactive B cells at the molecular level, the rearranged Ig heavy chain variable (V H ) genes from mouse splenic GC were examined (85,109). While most of the GC B cells in mice that received antigen alone expressed a single variable region gene, B cells of mice immunized with an antigen-MAb complex demonstrated heterogeneous V H gene expression, including nine different germ-line segments.…”

Repertoire of Antibody Response in Bone Marrow and the Memory Response Are Differentially Affected in Aging Mice

“…The details of the PCR reactions and sequences of the primers were published previously (15, 32). The PCR product was digested with the restriction enzymes, ligated to a plasmid, cloned in competent Escherichia coli, and sequenced as previously described (32).…”