Deficiency of somatic hypermutation of the antibody light chain is associated with increased frequency of severe respiratory tract infection in common variable immunodeficiency

Abstract

Reduced levels of somatic hypermutation (SHM) have recently been described in IgG-switched immunoglobulin genes in a minority of patients with common variable immunodeficiency (CVID), demonstrating a disruption of the normal linkage between isotype switch and SHM. To see if, irrespective of isotype, there is a tendency to use unmutated immunoglobulin genes in CVID, we studied SHM in light-chain transcripts using a V A27-specific restriction enzyme-based hot-spot mutation assay (IgREHMA). Hot-spot mutations were found in 48% (median; reference interval, 28%-62%) of transcripts from 53 healthy controls. Values were significantly lower in 31 patients (median, 7.5%; range, 0%-73%; P < .0000001) of whom 24 (77%) had levels below the reference interval. Low levels of SHM correlated with increased frequency of severe respiratory tract infection (SRTI; P < .005), but not with diarrhea (P ‫؍‬ .8). Mannose-binding lectin (MBL) deficiency also correlated with SRTI score (P ‫؍‬ .009). However, the correlation of SHM and SRTI was also seen when only patients with normal MBL genotypes were analyzed (n ‫؍‬ 18, P ‫؍‬ .006). A slight decline of mutated fractions over years was noted (P ‫؍‬ .01). This suggests that most patients with CVID fail to recruit affinity-maturated B cells, adding a qualitative deficiency to the quantitative deficiency characterizing these patients. (Blood. 2005;105:511-517)

Circulating CD21lowB cells in common variable immunodeficiency resemble tissue homing, innate-like B cells

“…SHM Analysis and KREC Assay. SHM in the V A27 transcript was analyzed using Ig-restriction enzyme-based hot-spot mutation assay (Ig-REHMA assay) as described by Andersen et al (13). Ig-REHMA assay for V3-20 gene as well as KREC assay was performed as described previously (14).…”

“…2A). In addition, we analyzed the presence of somatic hypermutations (SHM) as a sign for antigen driven selection by Ig-REHMA assays on the transcript and genomic level [Vk A27 (13) and Vk3-20 (14)] (Fig. 2B and data not shown).…”

Human memory B cells originate from three distinct germinal center-dependent and -independent maturation pathways

“…18,26 In brief, PCR was performed on genomic DNA using a hexachlorofluorescein phosphoramidite (HEX)-coupled IGKV3-20 intron forward primer and two 5-carboxyfluorescein-coupled IGKJ reverse primers recognizing all 5 IGKJ genes. The PCR products were digested by the KpnI and Fnu4HI restriction enzymes and run on an ABI Prism 3130 XL genetic analyzer.…”

B-cell replication history and somatic hypermutation status identify distinct pathophysiologic backgrounds in common variable immunodeficiency

“…20,35 In short, a PCR reaction was performed with a HEX-coupled V3-20 intron forward primer and 2 FAM-coupled J reverse primers recognizing all 5 J gene segments. The PCR products (500 bp) were digested with KpnI and Fnu4HI and run on an ABI3130XL capillary sequencer (Applied Biosystems).…”

“…20 In addition, SHM levels were determined by measuring the frequency of a mutated hot spot in rearranged V3-20 gene segments with an IgREHMA. 20,35 Transitional B cells are recent BM emigrants that have not undergone proliferation in healthy individuals. 20 In virtually all CVID patients, the replication history of transitional B cells was normal, including patients with reduced transitional B cells ( Figure 3A).…”