[Molecular mechanisms of B lymphocyte depletion by CD20 immunotherapy]

FCGR3A 158V/F polymorphism and response to frontline R-CHOP therapy in diffuse large B-cell lymphoma

The influence of Fc gamma receptor IIIA (FCGR3A) 158V/F polymorphisms on the response to rituximab (R) plus CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone; R-CHOP) therapy in diffuse large B-cell lymphoma (DLBCL) is uncertain. Thus, a retrospective study and a meta-analysis were performed to examine the possible correlation between FCGR3A 158V/F polymorphism and the response rate of R-CHOP regimen in patients with newly diagnosed DLBCL. The genotypes of FCGR3A 158V/F in 164 newly diagnosed DLBCL patients treated with R-CHOP were determined in this retrospective study. Additionally, a meta-analysis of current and previously published studies was conducted. Overall response rate (complete and partial response, ORR) and complete response rate (CR) were evaluated. The results of our retrospective study showed lack of correlation between FCGR3A 158V/F polymorphism and ORR (p=0.78) or CR (p=0.76) with R-CHOP therapy. A meta-analysis of 731 cases also showed lack of significant association of ORR and CR in all genetic models with FCGR3A 158V/F polymorphism. In survival analysis, the homozygous F genotype correlated with a shorter progression-free survival than that of non-F/F genotype (p=0.05), this was significant for the non-GC subset of DLBCL (p=0.04), but no association was found between overall survival and FCGR3A 158V/F polymorphism. Further analysis with nonsuperiority test (p<0.0001) suggested that FCGR3A 158V/F polymorphism was not associated with better ORR or CR in newly diagnosed DLBCL patient treated with R-CHOP. No clear relationship was found between FCGR3A 158V/F polymorphism and response to frontline R-CHOP therapy in patients with DLBCL.

Interleukin-35 induces regulatory B cells that suppress autoimmune disease

Interleukin 10-producing regulatory B-cells (Breg-cells) suppress autoimmune diseases while aberrant elevation of Breg-cells prevents sterilizing immunity, promotes carcinogenesis and cancer metastasis by converting resting CD4⁺ T-cells to regulatory T-cells (Tregs). It is therefore of interest to discover factors that induce Breg-cells. Here we show that IL-35 induces Breg-cells in-vivo and promotes their conversion to a unique Breg subset that produces IL-35 (IL-35⁺Breg). Treatment of mice with IL-35 conferred protection from uveitis and mice lacking IL-35 or defective in IL-35-signaling produced less Breg-cells and developed severe uveitis. Ex-vivo generated Breg-cells also suppressed uveitis by inhibiting pathogenic Th17/Th1 while promoting Tregs expansion. We further show that IL-35 induced the conversion of human B-cells into Breg-cells and suppressed uveitis by activating STAT1/STAT3 through IL-35-Receptor comprising IL-12Rβ2/IL-27Rα subunits. Discovery that IL-35 converts human B-cells into Breg-cells, allows ex-vivo production of autologous Breg-cells for immunotherapy and investigating Breg/IL-35⁺Breg cells roles in autoimmune diseases and cancer.

HLA class I antibodies trigger increased adherence of monocytes to endothelial cells by eliciting an increase in endothelial P-selectin and, depending on subclass, by engaging FcγRs

Ab-mediated rejection (AMR) of solid organ transplants is characterized by intragraft macrophages. It is incompletely understood how donor-specific Ab binding to graft endothelium promotes monocyte adhesion, and what, if any, contribution is made by the Fc region of the Ab. We investigated the mechanisms underlying monocyte recruitment by HLA class I (HLA I) Ab-activated endothelium. We used a panel of murine mAbs of different subclasses to crosslink HLA I on human aortic, venous, and microvascular endothelial cells and measured the binding of human monocytic cell lines and peripheral blood monocytes. Both anti-HLA I murine (m)IgG1 and mIgG2a induced endothelial P-selectin, which was required for monocyte adhesion to endothelium irrespective of subclass. mIgG2a but not mIgG1 could bind human FcγRs. Accordingly, HLA I mIgG2a but not mIgG1 treatment of endothelial cells significantly augmented recruitment, predominantly through FcγRI, and, to a lesser extent, FcγRIIa. Moreover, HLA I mIgG2a promoted firm adhesion of monocytes to ICAM-1 through Mac-1, which may explain the prominence of monocytes during AMR. We confirmed these observations using human HLA allele-specific mAbs and IgG purified from transplant patient sera. HLA I Abs universally elicit endothelial exocytosis leading to monocyte adherence, implying that P-selectin is a putative therapeutic target to prevent macrophage infiltration during AMR. Importantly, the subclass of donor-specific Ab may influence its pathogenesis. These results imply that human IgG1 and human IgG3 should have a greater capacity to trigger monocyte infiltration into the graft than IgG2 or IgG4 due to enhancement by FcγR interactions.

Regulatory B cells play a key role in immune system balance

Regulatory B cells (Bregs) may act earlier than regulatory T cells (Tregs) and may play as important a role in autoimmune and allergic diseases. Obstacles to the investigation of Bregs are the same as those encountered for Tregs: the regulatory effects are short-lived in some cases, there is no consistent phenotype (C5 expression is neither indispensable nor sufficient), differences exist across species (e.g., between humans and mice), and there are a number of suppression modalities (IL-10, TGF-beta, expression of proapoptotic membrane molecules) that vary across Breg subtypes. The Breg subtypes may be homologous to the Treg subtypes (Br1 cells expressing IL-10, Br3 cells expressing TGF-beta, and B-Foxp3 cells), although the Br1 subtype seems to predominate. Nevertheless, differences with Treg cells may exist: Breg activation may chiefly involve the toll-like receptors rather than the antigen receptor; and Bregs act earlier, facilitating the recruitment of Tregs then disappearing once the Tregs become operational. Bregs make a major contribution to autoimmune disorders associated with several forms of immune deficiency, as well as to the absence of transplant rejection when there is a strong B cell response. Breg deficiencies have been reported in lupus, and the disappointing effects in this disease of treatments designed to inhibit the B cell response may be related to further Breg impairment. In several animal models, Breg stimulation is effective in correcting a variety of autoimmune disorders, most notably those initiated in the mucous membranes. Research into the interactions between the gut microbiota and Bregs holds considerable promise.

Refractory antineutrophil cytoplasmic antibody-associated vasculitis successfully treated with rituximab: a case report

A 63-year-old-man was diagnosed in March 2002 with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis because of mononeuritis multiplex, interstitial pneumonia and a positive finding for myeloperoxidase (MPO)-ANCA. Although treated with prednisolone and oral cyclophosphamide, he suffered repeated remission and deterioration of his conditon, which was complicated by hypertrophic pachymeningitis and sinusitis. In July 2006, he was diagnosed with an exacerbation of ANCA-associated vasculitis because of pyrexia, general malaise, numbness in his face and legs, and elevated serum CRP level. Steroid pulse therapy was thus initiated and the patient's clinical symptoms improved. However, serum CRP levels elevated again (5.18 mg/dl) in September 2006. We began administration of rituximab (500 mg/bodyx4 times) in November 2006 and his symptom and laboratory data significantly improved. The dose of prednisolone was slowly decreased without suffering a relapse. Rituximab has been administered every one year, and good disease control has been achieved. Diagnosis of Wegener's granulomatosis was made from the findings of a nodular lesion in the left lung. Rituximab should be considered for patients with refractory ANCA-associated vasculitis.