Precocious Interleukin 21 Expression in Naive Mice Identifies a Natural Helper Cell Population in Autoimmune Disease

Thymflammation: The Role of a Constitutively Active Inflammatory Network and "Ectopic" Cell Types in the Thymus in the Induction of T Cell Tolerance and Beyond

The thymus exhibits constitutive activation of nearly all major inflammatory pathways, including sterile MyD88-dependent signaling and interferon production by mTECs, the presence of cellular and molecular components of type 1, type 2, and type 3 responses, as well as sustained B cell activation. The reasons for the existence of such a complex constitutively active inflammatory network at the site of T cell development-where the initial pathogen encounter is unlikely-have remained enigmatic. We propose that this inflammatory thymic 'ecosystem' has evolved to promote immunological tolerance to 'inflammatory self'-endogenous molecules absent from most peripheral tissues at steady state but upregulated during pathogen invasion. The spatial and temporal overlap with pathogen presence makes the discrimination of the inflammatory self from pathogen-derived molecules a unique challenge for the adaptive immune system. The frequent occurrence of diseases associated with autoantibodies against proinflammatory cytokines underscores the persistent risk of these molecules being misidentified as foreign. Their abundant representation in the thymus, therefore, is likely to be critical for maintaining tolerance. This review explores current insights into the thymic inflammatory network, its cellular and molecular constituents, and their role in the induction of T cell tolerance.

Investigation of high-mobility group box 1 variants with lymph node status and colorectal cancer risk

BACKGROUND

Accumulating studies indicated that maintain nuclei homeostasis was deemed to the protective factors for the occurrence of cancer. Thus, high-mobility group box 1 (HMGB1) might influence the risk and poorer prognoses of colorectal cancer (CRC).

AIM

This study was designed to investigate whether HMGB1 polymorphisms influence the risk and lymph node metastasis (LNM) of CRC.

METHODS

Firstly, we designed an investigation with 1003 CRC patients and 1303 cancer-free controls to observe whether HMGB1 rs1412125 T > C and rs1045411 C > T SNPs could influence the risk of cancer. Subsequently, we carried out a correlation-analysis to assess whether these SNPs could alter the risk of LNM.

RESULTS

The current investigation suggested a relationship of HMGB1 rs1412125 SNP with the increased susceptibility of CRC. In a subgroup analysis, our findings suggested that this SNP could enhance an occurrence of CRC in ≥ 61 years, non-drinker and body mass index < 24 kg/m2 subgroups. However, we found that there was null association between HMGB1 rs1412125 SNP and LNM, even in different CRC region. These observations were confirmed by calculating the power value (more than 0.8). The association of HMGB1 rs1045411 C > T SNP with CRC risk and LNM was not found in any compare.

CONCLUSION

This study highlights a possible association between HMGB1 rs1412125 polymorphism and the increased risk of CRC. In the future, more studies should be conducted to explore HMGB1 rs1412125 polymorphism in relation to CRC development.

CD4 T Cell-Derived IL-21 Is Critical for Sustaining Plasmodium Infection-Induced Germinal Center Responses and Promoting the Selection of Memory B Cells with Recall Potential

Development of Plasmodium-specific humoral immunity is critically dependent on CD4 Th cell responses and germinal center (GC) reactions during blood-stage Plasmodium infection. IL-21, a cytokine primarily produced by CD4 T cells, is an essential regulator of affinity maturation, isotype class-switching, B cell differentiation, and maintenance of GC reactions in response to many infection and immunization models. In models of experimental malaria, mice deficient in IL-21 or its receptor IL-21R fail to develop memory B cell populations and are not protected against secondary infection. However, whether sustained IL-21 signaling in ongoing GCs is required for maintaining GC magnitude, organization, and output is unclear. In this study, we report that CD4+ Th cells maintain IL-21 expression after resolution of primary Plasmodium yoelii infection. We generated an inducible knockout mouse model that enabled cell type-specific and timed deletion of IL-21 in peripheral, mature CD4 T cells. We found that persistence of IL-21 signaling in active GCs had no impact on the magnitude of GC reactions or their capacity to produce memory B cell populations. However, the memory B cells generated in the absence of IL-21 exhibited reduced recall function upon challenge. Our data support that IL-21 prevents premature cellular dissolution within the GC and promotes stringency of selective pressures during B cell fate determination required to produce high-quality Plasmodium-specific memory B cells. These data are additionally consistent with a temporal requirement for IL-21 in fine-tuning humoral immune memory responses during experimental malaria.

B cells orchestrate tolerance to the neuromyelitis optica autoantigen AQP4

Neuromyelitis optica is a paradigmatic autoimmune disease of the central nervous system, in which the water-channel protein AQP4 is the target antigen1. The immunopathology in neuromyelitis optica is largely driven by autoantibodies to AQP42. However, the T cell response that is required for the generation of these anti-AQP4 antibodies is not well understood. Here we show that B cells endogenously express AQP4 in response to activation with anti-CD40 and IL-21 and are able to present their endogenous AQP4 to T cells with an AQP4-specific T cell receptor (TCR). A population of thymic B cells emulates a CD40-stimulated B cell transcriptome, including AQP4 (in mice and humans), and efficiently purges the thymic TCR repertoire of AQP4-reactive clones. Genetic ablation of Aqp4 in B cells rescues AQP4-specific TCRs despite sufficient expression of AQP4 in medullary thymic epithelial cells, and B-cell-conditional AQP4-deficient mice are fully competent to raise AQP4-specific antibodies in productive germinal-centre responses. Thus, the negative selection of AQP4-specific thymocytes is dependent on the expression and presentation of AQP4 by thymic B cells. As AQP4 is expressed in B cells in a CD40-dependent (but not AIRE-dependent) manner, we propose that thymic B cells might tolerize against a group of germinal-centre-associated antigens, including disease-relevant autoantigens such as AQP4.

Stepwise differentiation of follicular helper T cells reveals distinct developmental and functional states

Follicular helper T (Tfh) cells are essential for the formation of high affinity antibodies after vaccination or infection. Although the signals responsible for initiating Tfh differentiation from naïve T cells have been studied, the signals controlling sequential developmental stages culminating in optimal effector function are not well understood. Here we use fate mapping strategies for the cytokine IL-21 to uncover sequential developmental stages of Tfh differentiation including a progenitor-like stage, a fully developed effector stage and a post-effector Tfh stage that maintains transcriptional and epigenetic features without IL-21 production. We find that progression through these stages are controlled intrinsically by the transcription factor FoxP1 and extrinsically by follicular regulatory T cells. Through selective deletion of Tfh stages, we show that these cells control antibody dynamics during distinct stages of the germinal center reaction in response to a SARS-CoV-2 vaccine. Together, these studies demonstrate the sequential phases of Tfh development and how they promote humoral immunity.

IL-21 is required for the maintenance and pathogenesis of murine Vγ4+ IL-17-producing γδT cells

Murine IL-17-producing γδT (γδT17) cells are divided into two subsets: natural γδT17 (nγδT17) cells, whose development is restricted to the fetal thymus, and inducible γδT17 cells, which require antigen exposure for their IL-17 production and are presumed to develop from Rorc + Il17a - CCR9 + immature γδT17 cells in the adult thymus and whose T cell receptor (TCR) is biased toward Vγ4. Although IL-23 is known to be involved in developing γδT17 cells, the roles of other cytokines, such as IL-21, which is involved in developing Th17 cells like IL-23, in the development, maintenance, and pathophysiology of γδT17 cells remain unknown. Here, we show that IL-21 is dispensable for the fetal thymic development of nγδT17 cells but is required for the peripheral maintenance of Vγ4+nγδT17 cells. Upon stimulation with γδTCR, IL-1 plus IL-21 induces the proliferation of Vγ4+nγδT17 cells via STAT3 as effectively as IL-1 plus IL-23. Using bone marrow chimeric mice, we demonstrated that immature γδT17 cells are produced de novo in the adult mice from donor adult bone marrow cells and that IL-21 is dispensable for their development. Instead, IL-21 is required to expand newly induced Vγ4+γδT17 cells in the periphery upon immunization. Finally, using adoptive transfer experiments of γδT17 cells, we found that IL-21 receptors on γδT17 cells are involved in maintaining Vγ4+γδT17 cells, subsequent infiltration of Th17 cells into the spinal cord, and exacerbation of experimental autoimmune encephalomyelitis. Collectively, IL-21 plays a vital role in the maintenance and pathogenesis of Vγ4+γδT17 cells.

Type III interferon drives thymic B cell activation and regulatory T cell generation

The activation of thymic B cells is critical for their licensing as antigen presenting cells and resulting ability to mediate T cell central tolerance. The processes leading to licensing are still not fully understood. By comparing thymic B cells to activated Peyer's patch B cells at steady state, we found that thymic B cell activation starts during the neonatal period and is characterized by TCR/CD40-dependent activation, followed by immunoglobulin class switch recombination (CSR) without forming germinal centers. Transcriptional analysis also demonstrated a strong interferon signature, which was not apparent in the periphery. Thymic B cell activation and CSR were primarily dependent on type III IFN signaling, and loss of type III IFN receptor in thymic B cells resulted in reduced thymocyte regulatory T cell (Treg) development. Finally, from TCR deep sequencing, we estimate that licensed B cells induce development of a substantial fraction of the Treg cell repertoire. Together, these findings reveal the importance of steady-state type III IFN in generating licensed thymic B cells that induce T cell tolerance to activated B cells.

Thymic changes as a contributing factor in the increased susceptibility of old Albino Oxford rats to EAE development

The study was aimed to examine putative contribution of thymic involution to ageing-associated increase in susceptibility of Albino Oxford (AO) rats to the development of clinical EAE, and vice versa influence of the disease on the progression of thymic involution. To this end we examined (i) the parameters of thymocyte negative selection efficacy, the thymic generation of CD4+CD25+Foxp3+ T regulatory cells (Tregs) and thymic capacity to instruct/predetermine IL-17-producing T-cell differentiation, and thymopietic efficacy-associated accumulation of "inflammescent" cytotoxic CD28- T cells in the periphery, and (ii) the key underlying mechanisms in young and old non-immunised AO rats and their counterparts immunised for EAE (on the 16^th day post-immunisation when the disease in old rats reached the plateau) using flow cytometry analysis and/or RT-qPCR. It was found that thymic involution impairs: (i) the efficacy of negative selection (by affecting thymocyte expression of CD90, negative regulator of selection threshold and the expression of thymic stromal cell integrity factors) and (ii) Treg generation (by diminishing expression of cytokines supporting their differentiation/maturation). Additionally, the results suggest that thymic involution facilitates CD8+ T-cell differentiation into IL-17-producing cells (previously linked to the development of clinical EAE in old AO rats). Furthermore, they confirmed that ageing-related decrease in thymic T-cell output (as indicated by diminished frequency of recent thymic emigrants in peripheral blood) resulted in the accumulation of CD28- T cells in peripheral blood and, upon immunisation, in the target organ. On the other hand, the development of EAE (most likely by increasing circulatory levels of proinflammatory cytokines) contributed to the decline in thymic output of T cells, including Tregs, and thereby to the progression/maintenance of clinical EAE. Thus, in AO rats thymic involution via multi-layered mechanisms may favour the development of clinically manifested autoimmunity, which, in turn, precipitates the thymus atrophy.

Mitochondrial regulation of acute extrafollicular B-cell responses to COVID-19 severity

BACKGROUND

Patients with COVID-19 display a broad spectrum of manifestations from asymptomatic to life-threatening disease with dysregulated immune responses. Mechanisms underlying the detrimental immune responses and disease severity remain elusive.

METHODS

We investigated a total of 137 APs infected with SARS-CoV-2. Patients were divided into mild and severe patient groups based on their requirement of oxygen supplementation. All blood samples from APs were collected within three weeks after symptom onset. Freshly isolated PBMCs were investigated for B cell subsets, their homing potential, activation state, mitochondrial functionality and proliferative response. Plasma samples were tested for cytokine concentration, and titer of Nabs, RBD-, S1-, SSA/Ro- and dsDNA-specific IgG.

RESULTS

While critically ill patients displayed predominantly extrafollicular B cell activation with elevated inflammation, mild patients counteracted the disease through the timely induction of mitochondrial dysfunction in B cells within the first week post symptom onset. Rapidly increased mitochondrial dysfunction, which was caused by infection-induced excessive intracellular calcium accumulation, suppressed excessive extrafollicular responses, leading to increased neutralizing potency index and decreased inflammatory cytokine production. Patients who received prior COVID-19 vaccines before infection displayed significantly decreased extrafollicular B cell responses and mild disease.

CONCLUSION

Our results reveal an immune mechanism that controls SARS-CoV-2-induced detrimental B cell responses and COVID-19 severity, which may have implications for viral pathogenesis, therapeutic interventions and vaccine development.

Translational regulation of TFH cell differentiation and autoimmune pathogenesis

Little is known regarding T cell translational regulation. We demonstrate that T follicular helper (TFH) cells use a previously unknown mechanism of selective messenger RNA (mRNA) translation for their differentiation, role in B cell maturation, and in autoimmune pathogenesis. We show that TFH cells have much higher levels of translation factor eIF4E than non-TFH CD4+ T cells, which is essential for translation of TFH cell fate-specification mRNAs. Genome-wide translation studies indicate that modest down-regulation of eIF4E activity by a small-molecule inhibitor or short hairpin RN impairs TFH cell development and function. In mice, down-regulation of eIF4E activity specifically reduces TFH cells among T helper subtypes, germinal centers, B cell recruitment, and antibody production. In experimental autoimmune encephalomyelitis, eIF4E activity down-regulation blocks TFH cell participation in disease pathogenesis while promoting rapid remission and spinal cord remyelination. TFH cell development and its role in autoimmune pathogenesis involve selective mRNA translation that is highly druggable.

Tissue-resident CD4+ T helper cells assist the development of protective respiratory B and CD8+ T cell memory responses

Much remains unknown about the roles of CD4⁺ T helper cells in shaping localized memory B cell and CD8⁺ T cell immunity in the mucosal tissues. Here, we report that lung T helper cells provide local assistance for the optimal development of tissue-resident memory B and CD8⁺ T cells after the resolution of primary influenza virus infection. We have identified a population of T cells in the lung that exhibit characteristics of both follicular T helper and T_RM cells, and we have termed these cells as resident helper T (T_RH) cells. Optimal T_RH cell formation was dependent on transcription factors involved in T follicular helper and resident memory T cell development including BCL6 and Bhlhe40. We show that T_RH cells deliver local help to CD8⁺ T cells through IL-21-dependent mechanisms. Our data have uncovered the presence of a tissue-resident helper T cell population in the lung that plays a critical role in promoting the development of protective B cell and CD8⁺ T cell responses.

IL-21 in Homeostasis of Resident Memory and Exhausted CD8 T Cells during Persistent Infection

CD4 T cells guide the development of CD8 T cells into memory by elaborating mitogenic and differentiation factors and by licensing professional antigen-presenting cells. CD4 T cells also act to stave off CD8 T cell dysfunction during repetitive antigen stimulation in persistent infection and cancer by mitigating generation of exhausted T cells (T_EX). CD4 T cell help is also required for establishing and maintaining tissue-resident memory T cells (T_RM), the nonrecirculating memory T cell subset parked in nonlymphoid tissues to provide frontline defense against reinvading pathogens. Interleukin (IL)-21 is the signature cytokine secreted by follicular helper CD4 T cells (T_FH) to drive B cell expansion and differentiation in germinal centers to mount high-affinity, isotype class-switched antibodies. In several infection models, IL-21 has been identified as the CD4 T help needed for formation and survival of T_RM and T_EX. In this review, we will explore the different memory subsets of CD8 T cells in persistent infections, the metabolic profiles associated with each, and evidence documenting the importance of CD4 T cell-derived IL-21 in regulating CD8 T_RM and T_EX development, homeostasis, and function.

IL-21 from high-affinity CD4 T cells drives differentiation of brain-resident CD8 T cells during persistent viral infection

Development of tissue-resident memory (T_RM) CD8 T cells depends on CD4 T cells. In polyomavirus central nervous system infection, brain CXCR5^hi PD-1^hi CD4 T cells produce interleukin-21 (IL-21), and CD8 T cells lacking IL-21 receptors (IL21R^-/-) fail to become bT_RM IL-21⁺ CD4 T cells exhibit elevated T cell receptor (TCR) affinity and higher TCR density. IL21R^-/- brain CD8 T cells do not express CD103, depend on vascular CD8 T cells for maintenance, are antigen recall defective, and lack T_RM core signature genes. CD4 T cell-deficient and IL21R^-/- brain CD8 T cells show similar deficiencies in expression of genes for oxidative metabolism, and intrathecal delivery of IL-21 to CD4 T cell-depleted mice restores expression of electron transport genes in CD8 T cells to wild-type levels. Thus, high-affinity CXCR5^hi PD-1^hi CD4 T cells in the brain produce IL-21, which drives CD8 bT_RM differentiation in response to a persistent viral infection.

Regulatory T Cells Restrain Interleukin-2- and Blimp-1-Dependent Acquisition of Cytotoxic Function by CD4+ T Cells

In addition to helper and regulatory potential, CD4+ T cells also acquire cytotoxic activity marked by granzyme B (GzmB) expression and the ability to promote rejection of established tumors. Here, we examined the molecular and cellular mechanisms underpinning the differentiation of cytotoxic CD4+ T cells following immunotherapy. CD4+ transfer into lymphodepleted animals or regulatory T (Treg) cell depletion promoted GzmB expression by tumor-infiltrating CD4+, and this was prevented by interleukin-2 (IL-2) neutralization. Transcriptional analysis revealed a polyfunctional helper and cytotoxic phenotype characterized by the expression of the transcription factors T-bet and Blimp-1. While T-bet ablation restricted interferon-γ (IFN-γ) production, loss of Blimp-1 prevented GzmB expression in response to IL-2, suggesting two independent programs required for polyfunctionality of tumor-reactive CD4+ T cells. Our findings underscore the role of Treg cells, IL-2, and Blimp-1 in controlling the differentiation of cytotoxic CD4+ T cells and offer a pathway to enhancement of anti-tumor activity through their manipulation.

The γc Family of Cytokines: Basic Biology to Therapeutic Ramifications

The common cytokine receptor γ chain, γ_c, is a component of the receptors for interleukin-2 (IL-2), IL-4, IL-7, IL-9, IL-15, and IL-21. Mutation of the gene encoding γ_c results in X-linked severe combined immunodeficiency in humans, and γ_c family cytokines collectively regulate development, proliferation, survival, and differentiation of immune cells. Here, we review the basic biology of these cytokines, highlighting mechanisms of signaling and gene regulation that have provided insights for immunodeficiency, autoimmunity, allergic diseases, and cancer. Moreover, we discuss how studies of this family stimulated the development of JAK3 inhibitors and present an overview of current strategies targeting these pathways in the clinic, including novel antibodies, antagonists, and partial agonists. The diverse roles of these cytokines on a range of immune cells have important therapeutic implications.

Investigation of multi-trait associations using pathway-based analysis of GWAS summary statistics

Background

Genome-wide association studies (GWAS) have been successful in identifying disease-associated genetic variants. Recently, an increasing number of GWAS summary statistics have been made available to the research community, providing extensive repositories for studies of human complex diseases. In particular, cross-trait associations at the genetic level can be beneficial from large-scale GWAS summary statistics by using genetic variants that are associated with multiple traits. However, direct assessment of cross-trait associations using susceptibility loci has been challenging due to the complex genetic architectures in most diseases, calling for advantageous methods that could integrate functional interpretation and imply biological mechanisms.

Results

We developed an analytical framework for systematic integration of cross-trait associations. It incorporates two different approaches to detect enriched pathways and requires only summary statistics. We demonstrated the framework using 25 traits belonging to four phenotype groups. Our results revealed an average of 54 significantly associated pathways (ranged between 18 and 175) per trait. We further proved that pathway-based analysis provided increased power to estimate cross-trait associations compared to gene-level analysis. Based on Fisher’s Exact Test (FET), we identified a total of 24 (53) pairs of trait-trait association at adjusted p_FET < 1 × 10^− 3 (p_FET < 0.01) among the 25 traits. Our trait-trait association network revealed not only many relationships among the traits within the same group but also novel relationships among traits from different groups, which warrants further investigation in future.

Conclusions

Our study revealed that risk variants for 25 different traits aggregated in particular biological pathways and that these pathways were frequently shared among traits. Our results confirmed known mechanisms and also suggested several novel insights into the etiology of multi-traits.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5373-7) contains supplementary material, which is available to authorized users.

Integration of T-cell receptor, Notch and cytokine signals programs mouse γδ T-cell effector differentiation

γδ T‐cells perform a wide range of tissue‐ and disease‐specific functions that are dependent on the effector cytokines produced by these cells. However, the aggregate signals required for the development of interferon‐γ (IFNγ) and interleukin‐17 (IL‐17) producing γδ T‐cells remain unknown. Here, we define the cues involved in the functional programming of γδ T‐cells, by examining the roles of T‐cell receptor (TCR), Notch, and cytokine‐receptor signaling. KN6 γδTCR‐transduced Rag2^−/− T‐cell progenitors were cultured on stromal cells variably expressing TCR and Notch ligands, supplemented with different cytokines. We found that distinct combinations of these signals are required to program IFNγ versus IL‐17 producing γδ T‐cell subsets, with Notch and weak TCR ligands optimally enabling development of γδ17 cells in the presence of IL‐1β, IL‐21 and IL‐23. Notably, these cytokines were also shown to be required for the intrathymic development of γδ17 cells. Together, this work provides a framework of how signals downstream of TCR, Notch and cytokine receptors integrate to program the effector function of IFNγ and IL‐17 producing γδ T‐cell subsets.

Induction of Hypergammaglobulinemia and Autoantibodies by Salmonella Infection in MyD88-Deficient Mice

Growing evidence indicates a link between persistent infections and the development of autoimmune diseases. For instance, the inability to control Salmonella infection due to defective toll-like receptor (TLR)/myeloid differentiation primary response 88 (MyD88) signaling has linked the development of persistent infections to a breakdown in B cell tolerance. However, the extent of immune dysregulation in the absence of TLR-MyD88 signaling remains poorly characterized. Here, we show that MyD88^−/− mice are unable to eliminate attenuated Salmonella enterica serovar Typhimurium, even when challenged with a low-dose inoculum (200 CFUs/mouse), developing a persistent and progressive infection when compared to wild-type (MyD88^+/+) animals. The splenic niche of MyD88^−/− mice revealed increased counts of activated, Sca-1-positive, myeloid subpopulations highly expressing BAFF during persistent Salmonella infection. Likewise, the T cell compartment of Salmonella-infected MyD88^−/− mice showed increased levels of CD4⁺ and CD8⁺ T cells expressing Sca-1 and CD25 and producing elevated amounts of IL-4, IL-10, and IL-21 in response to CD3/CD28 stimulation. This was associated with increased Tfh cell differentiation and the presence of CD4⁺ T cells co-expressing IFN-γ/IL-4 and IFN-γ/IL-10. Noteworthy, infected MyD88^−/− mice had enhanced serum titers of both anti-Salmonella antibodies as well as autoantibodies directed against double-stranded DNA, thyroglobulin, and IgG rheumatoid factor, positive nuclear staining with HEp-2 cells, and immune complex deposition in the kidneys of MyD88^−/− mice infected with live but not heat-killed Salmonella. Infection with other microorganisms (Acinetobacter baumanii, Streptococcus agalactiae, or Escherichia coli) was unable to trigger the autoimmune phenomenon. Our findings suggest that dysregulation of the immune response in the absence of MyD88 is pathogen-dependent and highlight potentially important genotype–environmental factor correlations.

Relative Contributions of B Cells and Dendritic Cells from Lupus-Prone Mice to CD4+ T Cell Polarization

Mouse models of lupus have shown that multiple immune cell types contribute to autoimmune disease. This study sought to investigate the involvement of B cells and dendritic cells in supporting the expansion of inflammatory and regulatory CD4⁺ T cells that are critical for lupus pathogenesis. We used lupus-prone B6.NZM2410.Sle1.Sle2.Sle3 (TC) and congenic C57BL/6J (B6) control mice to investigate how the genetic predisposition of these two cell types controls the activity of normal B6 T cells. Using an allogeneic in vitro assay, we showed that TC B1-a and conventional B cells expanded Th17 cells significantly more than their B6 counterparts. This expansion was dependent on CD86 and IL-6 expression and mapped to the Sle1 lupus-susceptibility locus. In vivo, TC B cells promoted greater differentiation of CD4⁺ T cells into Th1 and follicular helper T cells than did B6 B cells, but they limited the expansion of Foxp3 regulatory CD4⁺ T cells to a greater extent than did B6 B cells. Finally, when normal B6 CD4⁺ T cells were introduced into Rag1^-/- mice, TC myeloid/stromal cells caused their heightened activation, decreased Foxp3 regulatory CD4⁺ T cell differentiation, and increased renal infiltration of Th1 and Th17 cells in comparison with B6 myeloid/stromal cells. The results show that B cells from lupus mice amplify inflammatory CD4⁺ T cells in a nonredundant manner with myeloid/stromal cells.