Dendritic Cells Regulate Extrafollicular Autoreactive B Cells via T Cells Expressing Fas and Fas Ligand.

The extrafollicular (EF) plasmablast response to self-antigens that contain Toll-like receptor (TLR) ligands is prominent in murine lupus models and some bacterial infections, but the inhibitors and activators involved have not been fully delineated. Here, we used two conventional dendritic cell (cDC) depletion systems to investigate the role of cDCs on a classical TLR-dependent autoreactive EF response elicited in rheumatoid-factor B cells by DNA-containing immune complexes. Contrary to our hypothesis, cDC depletion amplified rather than dampened the EF response in Fas-intact but not Fas-deficient mice. Further, we demonstrated that cDC-dependent regulation requires Fas and Fas ligand (FasL) expression by T cells, but not Fas expression by B cells. Thus, cDCs activate FasL-expressing T cells that regulate Fas-expressing extrafollicular helper T (Tefh) cells. These studies reveal a regulatory role for cDCs in B cell plasmablast responses and provide a mechanistic explanation for the excess autoantibody production observed in Fas deficiency.

The Extracellular Domains of IgG1 and T Cell-Derived IL-4/IL-13 Are Critical for the Polyclonal Memory IgE Response In Vivo.

IgE-mediated activation of mast cells and basophils contributes to protective immunity against helminths but also causes allergic responses. The development and persistence of IgE responses are poorly understood, which is in part due to the low number of IgE-producing cells. Here, we used next generation sequencing to uncover a striking overlap between the IgE and IgG1 repertoires in helminth-infected or OVA/alum-immunized wild-type BALB/c mice. The memory IgE response after secondary infection induced a strong increase of IgE+ plasma cells in spleen and lymph nodes. In contrast, germinal center B cells did not increase during secondary infection. Unexpectedly, the memory IgE response was lost in mice where the extracellular part of IgG1 had been replaced with IgE sequences. Adoptive transfer studies revealed that IgG1+ B cells were required and sufficient to constitute the memory IgE response in recipient mice. T cell-derived IL-4/IL-13 was required for the memory IgE response but not for expansion of B cells from memory mice. Together, our results reveal a close relationship between the IgE and IgG1 repertoires in vivo and demonstrate that the memory IgE response is mainly conserved at the level of memory IgG1+ B cells. Therefore, targeting the generation and survival of allergen-specific IgG1+ B cells could lead to development of new therapeutic strategies to treat chronic allergic disorders.

Basophil-mediated protection against gastrointestinal helminths requires IgE-induced cytokine secretion.

Basophils orchestrate protection against reinfections with gastrointestinal helminths and ticks, but the underlying mechanisms remain elusive. We investigated the role of Fc receptors on basophils, the antibody isotypes IgG1 and IgE, and basophil-derived IL-4/IL-13 during challenge infections with Heligmosomoides polygyrus and Nippostrongylus brasiliensis. Using mixed bone marrow chimeras, we found that activating Fc receptors on basophils were required for protective immunity but not for regulation of basophil homeostasis. Furthermore, rapid worm expulsion was impaired in IgE-deficient but not in IgG1-deficient mice. Basophils promoted the recruitment of other effector cells into the small intestine and induced expression of the antihelminthic proteins resistin-like molecule ß and mucin 5ac. Selective deletion of IL-4/IL-13 in basophils resulted in impaired worm expulsion. Collectively, our results indicate that IgE-mediated activation of basophils and the release of basophil-derived IL-4/IL-13 are critical steps in protective immunity against helminths. Therefore, development of effective vaccines against helminths should consider boosting the IL-4/IgE/basophil axis of the immune system.

Swiprosin-1/EFhd2 limits germinal center responses and humoral type 2 immunity.

Activated B cells are selected for in germinal centers by regulation of their apoptosis. The Ca2+ -binding cytoskeletal adaptor protein Swiprosin-1/EFhd2 (EFhd2) can promote apoptosis in activated B cells. We therefore hypothesized that EFhd2 might limit humoral immunity by repressing both the germinal center reaction and the expected enhancement of immune responses in the absence of EFhd2. Here, we established EFhd2(-/-) mice on a C57BL/6 background, which revealed normal B- and T-cell development, basal Ab levels, and T-cell independent type 1, and T-cell independent type 2 responses. However, T cell-dependent immunization with sheep red blood cells and infection with the helminth Nippostrongylus brasiliensis (N.b) increased production of antibodies of multiple isotypes, as well as germinal center formation in EFhd2(-/-) mice. In addition, serum IgE levels and numbers of IgE+ plasma cells were strongly increased in EFhd2(-/-) mice, both after primary as well as after secondary N.b infection. Finally, mixed bone marrow chimeras unraveled an EFhd2-dependent B cell-intrinsic contribution to increased IgE plasma cell numbers in N.b-infected mice. Hence, we established a role for EFhd2 as a negative regulator of germinal center-dependent humoral type 2 immunity, with implications for the generation of IgE.

B-cell-intrinsic STAT6 signaling controls germinal center formation.

Infection with helminths and exposure to antigens induce a strong type 2 immune response resulting in the secretion of the cytokines IL-4 and IL-13 by CD4(+) T cells and several innate cell types. IL-4 and IL-13 promote class switch recombination to IgG1 and IgE while their role for germinal center (GC) formation is poorly understood. We found a dramatic reduction in the numbers of GC B cells when investigating different type 2 immune responses in IL-4/IL-13-deficient mice. IL-4/IL-13 from T cells located outside B-cell follicles was sufficient for GC formation. We further revealed that IL-4/IL-13 acts directly on B cells for the formation of a robust GC response. The frequency of apoptotic GC B cells was not altered in the absence of IL-4/IL-13 and proliferation was even enhanced. However, deficiency of signal transducer and activator of transcription 6 signaling in B cells resulted in failure to downregulate the chemotactic receptor Gpr183 (Ebi2) and downregulation of this receptor has been shown to be essential for proper GC B-cell differentiation. Thus, T-cell-derived extrafollicular IL-4/IL-13 and signal transducer and activator of transcription 6-regulated genes in B cells play a critical role for orchestration of the GC response in type 2 immunity.

IgE knock-in mice suggest a role for high levels of IgE in basophil-mediated active systemic anaphylaxis.

Immunoglobulin E (IgE) production is tightly regulated at the cellular and genetic levels and is believed to be central to allergy development. At least two cellular pathways exist that lead to systemic anaphylaxis reactions in vivo: IgE-sensitized mast cells and IgG1-sensitized basophils. Passive anaphylaxis, by application of allergen and allergen-specific antibodies in mice, indicates a differential contribution of immunoglobulin isotypes to anaphylaxis. However, analysis of a dynamic immunization-mediated antibody response in anaphylaxis is difficult. Here, we generated IgE knock-in mice (IgE(ki) ), which express the IgE heavy chain instead of IgG1, in order to analyze the contribution of IgG1 and IgE to active anaphylaxis in vivo. IgE(ki) mice display increased IgE production both in vitro and in vivo. The sensitization of IgE(ki) mice by immunization followed by antigen challenge leads to increased anaphylaxis. Homozygous IgE(ki) mice, which lack IgG1 due to the knock-in strategy, are most susceptible to active systemic anaphylaxis. The depletion of basophils demonstrates their importance in IgE-mediated anaphylaxis. Therefore, we propose that an enhanced, antigen-specific, polyclonal IgE response, as is the case in allergic patients, is probably the most efficient way to sensitize basophils to contribute to systemic anaphylaxis in vivo.

The transcription factor GATA-3 controls cell fate and maintenance of type 2 innate lymphoid cells.

Innate lymphoid cells (ILCs) reside at mucosal surfaces and control immunity to intestinal infections. Type 2 innate lymphoid cells (ILC2s) produce cytokines such as IL-5 and IL-13, are required for immune defense against helminth infections, and are involved in the pathogenesis of airway hyperreactivity. Here, we have investigated the role of the transcription factor GATA-3 for ILC2 differentiation and maintenance. We showed that ILC2s and their lineage-specified bone marrow precursors (ILC2Ps), as identified here, were characterized by continuous high expression of GATA-3. Analysis of mice with temporary deletion of GATA-3 in all ILCs showed that GATA-3 was required for the differentiation and maintenance of ILC2s but not for RORγt(+) ILCs. Thus, our data demonstrate that GATA-3 is essential for ILC2 fate decisions and reveal similarities between the transcriptional programs controlling ILC and T helper cell fates.

Human endogenous retrovirus transcription profiles of the kidney and kidney-derived cell lines.

The human genome comprises approximately 8-9 % of human endogenous retroviruses (HERVs) that are transcribed with tissue specificity. However, relatively few organs have been examined in detail for individual differences in HERV transcription pattern, nor have tissue-to-cell culture comparisons been frequently performed. Using an HERV-specific DNA microarray, a core HERV transcription profile was established for the human kidney comparing 10 tissue samples. This core represents HERV groups expressed uniformly or nearly so in non-tumour kidney tissue. The profiles obtained from non-tumour tissues were compared to 10 renal tumour tissues (renal cell carcinoma, RCC) derived from the same individuals and additionally, to 22 RCC cell lines. No RCC cell line or tumour-specific differences were observed, suggesting that HERV transcription is not altered in RCC. However, when comparing tissue transcription to cell line transcription, there were consistent differences. The differences were irrespective of cancer state and included cell lines derived from non-tumour kidney tissue, suggesting that a specific alteration of HERV transcription occurs when establishing cell lines. In contrast to previous publications, all known HERV-derived tumour antigens, including those identified in RCC, were expressed both in multiple RCC cell lines and several non-tumour tissue-derived cell lines, a result that contrasts with findings from patient samples. The results establish the core kidney transcription pattern of HERVs and reveal differences between cell culture lines and tissue samples.

Human renal cell carcinoma induces a dendritic cell subset that uses T-cell crosstalk for tumor-permissive milieu alterations.

Tissue dendritic cells (DCs) may influence the progression of renal cell carcinoma (RCC) by regulating the functional capacity of antitumor effector cells. DCs and their interaction with T cells were analyzed in human RCC and control kidney tissues. The frequency of CD209(+) DCs in RCCs was found to be associated with an unfavorable T(H)1 cell balance in the tissue and advanced tumor stages. The CD209(+) DCs in RCC were unusual because most of them co-expressed macrophage markers (CD14, CD163). The phenotype of these enriched-in-renal-carcinoma DCs (ercDCs) could be reiterated in vitro by carcinoma-secreted factors (CXCL8/IL-8, IL-6, and vascular endothelial growth factor). ErcDCs resembled conventional DCs in costimulatory molecule expression and antigen cross-presentation. They did not suppress cognate cytotoxic T-lymphocyte function and did not cause CD3ζ down-regulation, FOXP3 induction, or T-cell apoptosis in situ or in vitro; thus, they are different from classic myeloid-derived suppressor cells. ErcDCs secreted high levels of metalloproteinase 9 and used T-cell crosstalk to increase tumor-promoting tumor necrosis factor α and reduce chemokines relevant for T(H)1-polarized lymphocyte recruitment. This modulation of the tumor environment exerted by ercDCs suggests an immunologic mechanism by which tumor control can fail without involving cytotoxic T-lymphocyte inhibition. Pharmacologic targeting of the deviated DC differentiation could improve the efficacy of immunotherapy against RCC.

T-cell receptor gene-modified T cells with shared renal cell carcinoma specificity for adoptive T-cell therapy.

PURPOSE: Adoptive therapy with genetically engineered T cells carrying redirected antigen specificity is a new option for the treatment of cancer. This approach is not yet available for metastatic renal cell carcinoma (RCC), due to the scarcity of therapeutically useful reagents. We analyzed tumor-infiltrating lymphocytes (TIL) from RCC to identify T-cell specificities with shared tumor-specific recognition to develop T-cell receptor (TCR)-engineered T lymphocytes for adoptive therapy of RCC. EXPERIMENTAL DESIGN: We established a T-cell clone from TIL that recognized a human leukocyte antigen (HLA)-A2-restricted tumor antigen. The TCR alpha- and beta-chain genes were isolated, modified by codon optimization and murinization, and retrovirally transduced into peripheral blood lymphocytes (PBL). A TCR-expressing indicator line (B3Z-TCR53) was established to screen for antigen prevalence in RCC, other malignancies, and normal cell counterparts. RESULTS: TCR53-engineered PBL recapitulated the specificity of the TIL and showed tumor-specific HLA-A2-restricted effector activities (IFN-gamma, tumor necrosis factor-alpha, interleukin-2, macrophage inflammatory protein-1beta, cytotoxicity). PBL-TCR53 of healthy donors and RCC patients exhibited similar transduction efficiency, expansion, and polyfunctional profile. Using B3Z-TCR53 cells, 130 tumor and normal cells were screened and shared TCR53 peptide: MHC expression was found in >60% of RCC and 25% of tumor lines of other histology, whereas normal tissue cells were not recognized. CONCLUSIONS: To date, TCR53 is the only TCR with shared HLA-A2-restricted recognition of RCC. It fulfills the criteria for utilization in TCR gene therapy and advances T cell-based immunotherapy to patients with RCC and other malignancies expressing the TCR ligand.