Induction of IgG₂ and IgG₄ B‐cell memory following sublingual immunotherapy for ryegrass pollen allergy

Abstract

Background: While treatment for atopic rhinitis is aimed mostly to relieve symptoms, only allergen-specific immunotherapy (AIT) is targeted to modify the natural history of allergic diseases. This results in sustained clinical tolerance, even when treatment has stopped. The immunomodulatory effects of AIT are attributed mainly to increased regulatory T-cell function and increased allergen-specific IgG 4 , yet little is known about the effect on the memory B-cell compartment. Objective:We aimed to examine the effects of AIT on the IgE-and IgG subclass-expressing memory B cells. Methods:We recruited 29 patients with atopic seasonal rhinoconjunctivitis and performed a longitudinal analysis of the peripheral immune compartment before, during, and after sublingual immunotherapy (SLIT) for allergy to temperate grass pollen, predominantly to ryegrass pollen (RGP; Lolium perenne). Using flow cytometry on peripheral blood mononuclear cells and serum immunoassays, we analyzed the effects of a 4 months preseasonal treatment regimen comprising two or three courses in consecutive years on circulating IgE + and IgG + memory B cells and allergen-specific Ig levels.Results: SLIT increased RGP-specific serum IgG 2 and IgG 4 , as well as the frequencies of IgG 2 + and IgG 4 + memory B cells, whereas no effect was observed on the IgE + memory B-cell compartment. Furthermore, SLIT enhanced proportions of regulatory T cells specific to RGP. These changes were associated with clinical improvement. Conclusion:Our data provide evidence for immunological effects of SLIT on B-cell memory. Skewing responses toward IgG 2 and IgG 4 subclasses might be a mechanism to suppress IgE-mediated allergic responses.

Recent developments and highlights in immune monitoring of allergen immunotherapy

“…59 Furthermore, paired analysis of IgG transcripts in ryegrass pollen-allergic patients before and after 3 years of SLIT showed that usage of IGHG2 and IGHG4 was increased within the total pool of unique IGHG transcripts. 33 Together, these studies demonstrate the potential of measuring changes in the IGH transcript repertoire that correlate with allergic disease and effects of treatment, and might be utilized as biomarkers. Similar approaches have been initiated for T-cell receptor beta (TRB) transcripts, where an increase in repertoire diversity was found in allergic individuals as compared to nonallergic controls.…”

“…In a recent study, during 3 years of SLIT for grass pollen, the frequency of IgE-expressing B cells within the total B-cell fraction was found to not change significantly, but using IgG subclass detecting reagents, the frequencies of IgG2-expressing B cells and IgG4-expressing B cells were found to be specifically increased following SLIT. 33 It appears that changes in the B-cell compartment are quite restricted, as despite early reports of more global changes involving transitional and naive mature B cells in atopic dermatitis, 126 these could not be replicated, 127 and do not appear to be affected by AIT. 33 The exception to this would be an increase in IL-10-expressing B cells, or Breg, which is associated with tolerance to bee venom and SLIT for grass pollen and HDM allergies.…”

“…Typically, after 1-7 days of culture, cytokine production in culture supernatant can be assessed to determine Th1/Th2 shifts and Treg involvement. 33,111 The advantage of in vitro stimulation is that allergen-specific cells can be examined subsequently based on the upregulation of activation markers (eg CD154…”

“…and CD137) or proliferation as assessed by dilution of labelling dyes. 33,112 Flow cytometry of activation markers can be combined with intracellular staining for cytokines and intranuclear staining for the Treg transcription factor FoxP3. The latter approach allows for single-cell measurements and multi-parameter analysis, which have been applied to demonstrate reduction in Th2 cells following SLIT for HDM 34 and grass pollen, 11 as well as plasticity of Th2 cells developing a Treg phenotype following oral AIT for peanut allergy.…”

“…113 Furthermore, allergen-specific Tregs have been shown to expand following AIT for HDM and grass pollen allergies thereby increasing the ratio of allergen-specific Tregs over effector T cells. 32,33,114,115 To facilitate translation towards routine measurements of T-cell biomarkers, immunophenotyping approaches have been developed that only use membrane markers and allow for direct ex vivo T-cell evaluation without in vitro cell culture. The CD4+CD25+CD127phenotype specifically distinguishes human Treg, 116,117 and these cells can be quantified in allergic patients 31 with increases following SLIT for grass pollen 11 and AIT in HDM-allergic individuals.…”