In this Review, Nicole Baumgarth describes the development and functions of B-1 cells. These innate-like B cells serve as the major source of natural antibody in mice, and can have important roles in defence against mucosal pathogens and in maintaining tissue homeostasis. During their development, B and T cells with self-reactive antigen receptors are generally deleted from the repertoire to avoid autoimmune diseases. Paradoxically, innate-like B-1 cells in mice are positively selected for self-reactivity and form a pool of long-lived, self-renewing B cells that produce most of the circulating natural IgM antibodies. This Review provides an overview of the developmental processes that shape the B-1 cell pool in mice, outlines the functions of B-1 cells in both the steady state and during host defence, and discusses possible functional B-1 cell homologues that exist in humans.

The double life of a B-1 cell: self-reactivity selects for protective effector functions

B cells play a central role in the immunopathogenesis of glomerulonephritides and transplant rejection. B cells secrete antibodies that contribute to tissue injury via multiple mechanisms. In addition, B cells contribute to disease pathogenesis in autoimmunity and alloimmunity by presenting antigens as well as providing costimulation and cytokines to T cells. B cells also play an immunomodulatory role in regulating the immune response by secreting cytokines that inhibit disease onset and/or progression. B cell–targeted approaches for treating immune diseases of the kidney and other organs have gained significant momentum. However, much remains to be understood about B-cell biology in order to determine the timing, duration, and context of optimal therapeutic response to B cell–targeted approaches. In this review, we discuss the multifaceted roles of B cells as enhancers and regulators of immunity with relevance to kidney disease and transplantation.

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B Cells, Antibodies, and More

Mucosal-associated invariant T (MAIT) cells are unique innate-like T cells that bridge innate and adaptive immunity. They are activated by conserved bacterial ligands derived from vitamin B biosynthesis and have important roles in defence against bacterial and viral infections. However, they can also have various deleterious and protective functions in autoimmune, inflammatory and metabolic diseases. MAIT cell involvement in a large spectrum of pathological conditions makes them attractive targets for potential therapeutic approaches. Mucosal-associated invariant T cells display innate, effector-like qualities and are involved, in various ways, in infectious and non-infectious diseases. Insights into their activation, tissue migration and function are revealing their beneficial and deleterious roles in disease.

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Mucosal-associated invariant T cells and disease.

Primary Glomerular Disease

IgA nephropathy frequently leads to progressive CKD. Although interest surrounds use of immunosuppressive agents added to standard therapy, several recent studies have questioned efficacy of these agents. Depleting antibody-producing B cells potentially offers a new therapy. In this open label, multicenter study conducted over 1-year follow-up, we randomized 34 adult patients with biopsy-proven IgA nephropathy and proteinuria >1 g/d, maintained on angiotensin-converting enzyme inhibitors or angiotensin receptor blockers with well controlled BP and eGFR<90 ml/min per 1.73 m2, to receive standard therapy or rituximab with standard therapy. Primary outcome measures included change in proteinuria and change in eGFR. Median baseline serum creatinine level (range) was 1.4 (0.8-2.4) mg/dl, and proteinuria was 2.1 (0.6-5.3) g/d. Treatment with rituximab depleted B cells and was well tolerated. eGFR did not change in either group. Rituximab did not alter the level of proteinuria compared with that at baseline or in the control group; three patients in each group had ≥50% reduction in level of proteinuria. Serum levels of galactose-deficient IgA1 or antibodies against galactose-deficient IgA1 did not change. In this trial, rituximab therapy did not significantly improve renal function or proteinuria assessed over 1 year. Although rituximab effectively depleted B cells, it failed to reduce serum levels of galactose-deficient IgA1 and antigalactose-deficient IgA1 antibodies. Lack of efficacy of rituximab, at least at this stage and severity of IgA nephropathy, may reflect a failure of rituximab to reduce levels of specific antibodies assigned salient pathogenetic roles in IgA nephropathy.

http://hwmaint.jasn.asnjournals.org/cgi/rapidpdf/ASN.2016060640v1.pdf

A Randomized, Controlled Trial of Rituximab in IgA Nephropathy with Proteinuria and Renal Dysfunction

The underlying mechanism of the protective and suppressive role of NKT cells in human tumor immunosurveillance remains to be fully elucidated. We show that the frequencies of CD8(+) NKT cells in patients with EBV-associated Hodgkin's lymphoma or nasopharyngeal carcinoma are significantly lower than those in healthy EBV carriers. These CD8(+) NKT cells in tumor patients are also functionally impaired. In human-thymus-severe combined immunodeficient (hu-thym-SCID) chimeras, EBV challenge efficiently promotes the generation of IFN-gamma-biased CD8(+) NKT cells. These cells are strongly cytotoxic, drive syngeneic T cells into a Th1 bias, and enhance T-cell cytotoxicity to EBV-associated tumor cells. Interleukin-4-biased CD4(+) NKT cells are predominately generated in unchallenged chimeras. These cells are noncytotoxic, drive syngeneic T cells into a Th2 bias, and do not affect T-cell cytotoxicity. In humanized xenogeneic tumor-transplanted hu-thym-SCID chimeras, adoptive transfer with EBV-induced CD8(+) NKT cells significantly suppresses tumorigenesis by EBV-associated malignancies. EBV-induced CD8(+) NKT cells are necessary and sufficient to enhance the T-cell immunity to EBV-associated malignancies in the hu-thym-SCID chimeras. CD4(+) NKT cells are synergetic with CD8(+) NKT cells, leading to a more pronounced T-cell antitumor response in the chimeras cotransferred with CD4(+) and CD8(+) NKT cells. Thus, immune reconstitution with EBV-induced CD8(+) NKT cells could be a useful strategy in management of EBV-associated malignancies.

https://cancerres.aacrjournals.org/content/canres/69/20/7935.full.pdf

EBV-induced human CD8+ NKT cells suppress tumorigenesis by EBV-associated malignancies.

The source of IgA and the mechanism for deposition of IgA in the mesangium remain unknown for primary IgA nephropathy. Because CD19(+)CD5(+) B cells are important producers of IgA and contribute to several autoimmune diseases, they may play an important role in IgA nephropathy. In this study, flow cytometry, quantitative PCR, and confocal microscopy were used to assess the frequency, distribution, Ig production, CD phenotypes, cytokine production, and sensitivity to apoptosis of CD19(+)CD5(+) B cells in the peripheral blood, peritoneal fluid, and kidney biopsies of 36 patients with primary IgA nephropathy. All patients with IgA nephropathy were significantly more likely to have CD19(+)CD5(+) B cells in the peripheral blood, peritoneal fluid, and kidney biopsies than were five control subjects and 10 patients with active systemic lupus erythematosus. The 33 patients who had IgA nephropathy and responded to treatment demonstrated a significant decrease in CD19(+)CD5(+) B cells in the peripheral blood, peritoneal fluid, and kidney (all P < 0.01). In the three patients who had IgA nephropathy and did not respond to treatment, the frequency of CD19(+)CD5(+) B cells did not change. CD19(+)CD5(+) B cells isolated from patients with untreated IgA nephropathy expressed higher levels of IgA, produced more IFN-gamma, and were more resistant to CD95L-induced apoptosis than cells isolated from control subjects and patients with lupus; these properties reversed with effective treatment of IgA nephropathy. In conclusion, these results strongly suggest that CD19(+)CD5(+) B cells play a prominent role in the pathogenesis of primary IgA nephropathy.

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CD19+CD5+ B Cells in Primary IgA Nephropathy

Background/aims Mucosa-associated T-lymphocyte (MAIT) cells that are selectively accumulated in the intestinal mucosa may be involved in immune regulation. MAIT cells are determined by their Vα7.2-Jα33 (human)/Vα19-Jα33 (mice) invariant chain. The encoding DNA sequences of Human Jα33 and mouse Jα33 are identical. In order to study the role of MAIT cells in IBD we produced anti-Jα33 antibody to detect MAIT cells in TNBS induced IBD models. Methodology Colitis was induced by TNBS in male BALB/c mice. Jα33+MAIT cells from normal mice were transferred into TNBS induced mice as donors. Colitis severity was evaluated clinically and histologically, under the condition of transferred Jα33+MAIT cells. Results The mRNA and protein expression levels of MAIT aTCR in the colonic mucosa were decreased after TNBS administration; Jα33+MAIT cells were aggregated in spleen after TNBS administration. The disease activity index (DAI) which was determined by weight loss, stool consistency and intestinal bleeding, increased after TNBS administration. Transferred Jα33+MAIT cells significantly degrade the increase in the disease activity index scores. Conclusions Taken together, the results indicated that the aggregation of Jα33+MAIT cells in intestinal mucosa improved TNBS-induced colitis. We conclude that Jα33+MAIT cells play a protective role in TNBS induced intestinal inflammation.

Jα33+ MAIT cells play a protective role in TNBS induced intestinal inflammation.

The reports on the origin of human CD8+ Vα24+ T-cell receptor (TCR) natural killer T (NKT) cells are controversial. The underlying mechanism that controls human CD4 versus CD8 NKT cell development is not well-characterized. In the present study, we have studied total 177 eligible patients and subjects including 128 healthy latent Epstein-Barr-virus(EBV)-infected subjects, 17 newly-onset acute infectious mononucleosis patients, 16 newly-diagnosed EBV-associated Hodgkin lymphoma patients, and 16 EBV-negative normal control subjects. We have established human-thymus/liver-SCID chimera, reaggregated thymic organ culture, and fetal thymic organ culture. We here show that the average frequency of total and CD8+ NKT cells in PBMCs from 128 healthy latent EBV-infected subjects is significantly higher than in 17 acute EBV infectious mononucleosis patients, 16 EBV-associated Hodgkin lymphoma patients, and 16 EBV-negative normal control subjects. However, the frequency of total and CD8+ NKT cells is remarkably increased in the acute EBV infectious mononucleosis patients at year 1 post-onset. EBV-challenge promotes CD8+ NKT cell development in the thymus of human-thymus/liver-SCID chimeras. The frequency of total (3% of thymic cells) and CD8+ NKT cells (∼25% of NKT cells) is significantly increased in EBV-challenged chimeras, compared to those in the unchallenged chimeras (<0.01% of thymic cells, CD8+ NKT cells undetectable, respectively). The EBV-induced increase in thymic NKT cells is also reflected in the periphery, where there is an increase in total and CD8+ NKT cells in liver and peripheral blood in EBV-challenged chimeras. EBV-induced thymic CD8+ NKT cells display an activated memory phenotype (CD69+CD45ROhiCD161+CD62Llo). After EBV-challenge, a proportion of NKT precursors diverges from DP thymocytes, develops and differentiates into mature CD8+ NKT cells in thymus in EBV-challenged human-thymus/liver-SCID chimeras or reaggregated thymic organ cultures. Thymic antigen-presenting EBV-infected dendritic cells are required for this process. IL-7, produced mainly by thymic dendritic cells, is a major and essential factor for CD8+ NKT cell differentiation in EBV-challenged human-thymus/liver-SCID chimeras and fetal thymic organ cultures. Additionally, these EBV-induced CD8+ NKT cells produce remarkably more perforin than that in counterpart CD4+ NKT cells, and predominately express CD8αα homodimer in their co-receptor. Thus, upon interaction with certain viruses, CD8 lineage-specific NKT cells are developed, differentiated and matured intrathymically, a finding with potential therapeutic importance against viral infections and tumors.

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EBV promotes human CD8 NKT cell development.

The purpose of this study is to introduce a methodology of the immunostaining of human lung tissues, followed by whole-slide digital scanning and image analysis. Digital scanning is a fast way to scan a stack of slides and produce digital images with high quality. It can produce concordant results with conventional light microscopy (CLM) by pathologists. Furthermore, the availability of digital images makes it possible that the same slide can be concurrently observed by multiple people. Moreover, digital images of slides can be stored in a database, which means the long-term deterioration of glass slides is avoided. The limitations of this technique are as follows. First, it needs high-quality prepared tissue and the original immunohistochemistry (IHC) slides without any damage or excess sealant residue. Second, tumor or nontumor areas should be specified by experienced pathologists before the analysis using software, in order to avoid any confusion about the tumor or nontumor areas during scoring. Third, the operator needs to control the color reproduction throughout the digitization process in whole-slide imaging.

Xiao Ruijing

Papers

EBV-induced human CD8+ NKT cells suppress tumorigenesis by EBV-associated malignancies.

CD19+CD5+ B Cells in Primary IgA Nephropathy

Jα33+ MAIT cells play a protective role in TNBS induced intestinal inflammation.

EBV promotes human CD8 NKT cell development.

Digital Analysis of Immunostaining of ZW10 Interacting Protein in Human Lung Tissues