S. Marieke van Ham

Adalimumab elicits a restricted anti-idiotypic antibody response in autoimmune patients resulting in functional neutralisation

Objectives Millions of patients worldwide are treated with therapeutic monoclonal antibodies. These biological therapeutics can be immunogenic, resulting in anti-drug antibody formation which leads to loss of response. Fully human biological agents, such as the anti-tumour necrosis factor α (anti-TNFα) antibody adalimumab, are considered to be weakly immunogenic, but anti-adalimumab antibodies (AAA) were recently detected in more than half of treated patients with rheumatoid arthritis (RA) within 28 weeks of treatment. A study was undertaken to determine the mechanism by which AAA lead to loss of response. Methods The specificity of the repertoire of AAA was investigated in a cohort of 50 AAA-positive RA patients. Inhibition experiments using TNFα and patient-derived anti-adalimumab monoclonal antibodies were performed. Results The antibody response against adalimumab is highly restricted: Fab fragments of a single monoclonal antibody specific for the idiotype of adalimumab inhibited 98.65% (25th–75th percentiles: 98.25–99.90) of the total anti-adalimumab reactivity in serum from 50 AAA-positive patients. The anti-adalimumab response was confined to the TNFα binding region of adalimumab, thereby neutralising its therapeutic efficacy. In line with this restricted specificity, small immune complexes were found in the circulation of AAA-forming patients. Conclusions The humoral immune response against adalimumab is highly restricted and limited to the idiotype of the therapeutic antibody. All antibodies result in functional neutralisation of the drug, thereby providing a mechanism by which AAA formation leads to clinical non-response.

IL-10-generated tolerogenic dendritic cells are optimal for functional regulatory T cell induction — A comparative study of human clinical-applicable DC

Tolerogenic dendritic cells (tDC) are a promising tool for specific cellular therapy to induce immunological tolerance in transplantation and autoimmunity. To date, most described tDC methods have not been converted into clinically applicable protocols and systematic comparison of required functional characteristics, i.e. migration and functional regulatory T cell (Treg) induction, is lacking. We compare clinical-grade tDC generated with vitamin D(3), IL-10, dexamethasone, TGFβ or rapamycin. For good migratory capacity and a stable phenotype, additional maturation of tDC was required. Maturation with a cocktail of TNFα, IL-1β and PGE(2) induced optimal migration. Importantly, all tDC showed a stable phenotype under pro-inflammatory conditions. Especially IL-10 DC showed most powerful tolerogenic characteristics with high IL-10 production and low T cell activation. Moreover, in a functional suppression assay only IL-10 DC induced Treg that strongly suppressed T cell reactivity. Thus, clinical-grade IL-10 DC show functional characteristics that make them best suited for tolerance-inducing therapies.

Molecular profiling of cytomegalovirus-induced human CD8 + T cell differentiation

CD8+ T cells play a critical role in the immune response to viral pathogens. Persistent human cytomegalovirus (HCMV) infection results in a strong increase in the number of virus-specific, quiescent effector-type CD8+ T cells with constitutive cytolytic activity, but the molecular pathways involved in the induction and maintenance of these cells are unknown. We show here that HCMV infection induced acute and lasting changes in the transcriptomes of virus-reactive T cells collected from HCMV-seropositive patients at distinct stages of infection. Enhanced cell cycle and metabolic activity was restricted to the acute phase of the response, but at all stages, HCMV-specific CD8+ T cells expressed the Th1-associated transcription factors T-bet (TBX21) and eomesodermin (EOMES), in parallel with continuous expression of IFNG mRNA and IFN-γ-regulated genes. The cytolytic proteins granzyme B and perforin as well as the fractalkine-binding chemokine receptor CX3CR1 were found in virus-reactive cells throughout the response. During HCMV latency, virus-specific CD8+ T cells lacked the typical features of exhausted cells found in other chronic infections. Persistent effector cell traits together with the permanent changes in chemokine receptor usage of virus-specific, nonexhausted, long-lived CD8+ T cells may be crucial to maintain lifelong protection from HCMV reactivation.

Hurdles in therapy with regulatory T cells.

Translating regulatory T cell therapy to the clinic in Europe is making progress but has remaining challenges. Improper activation of the immune system contributes to a variety of clinical conditions, including autoimmune and allergic diseases as well as solid organ and bone marrow transplantation. One approach to counteract this activation is through adoptive therapy with regulatory T cells (Tregs). Efforts to manufacture these cells have led to good maunfacturing practice–compliant protocols, and Treg products are entering early clinical trials. Here, we report the stance of the European Union Cooperation in Science and Technology Action BM1305, “Action to Focus and Accelerate Cell-based Tolerance-inducing Therapies—A FACTT,” which identifies hurdles hindering Treg clinical applications in Europe and provides possible solutions.

Class II-Associated Invariant Chain Peptide Expression on Myeloid Leukemic Blasts Predicts Poor Clinical Outcome

Effective antitumor responses need the activation of CD4+ T cells. MHC class II antigen presentation requires the release of class II-associated invariant chain peptide (CLIP) from the antigen-binding site. In antigen-presenting cells, human leukocyte antigen DM (HLA-DM; abbreviated DM in this article) catalyzes CLIP dissociation. In B cells, HLA-DO (DO) down-modulates DM function. Cell surface CLIP:HLA-DR (DR) ratio correlates to DO:DM ratio and the efficacy of antigen presentation. We examined 111 blood and bone marrow samples of patients with newly diagnosed acute myeloid leukemia (AML) for the expression of CLIP, DR, DM, and DO by flow cytometry. Patients with DR+/CLIP− blasts had a significant longer disease-free survival than patients with DR+/CLIP+ blasts. DO, until now believed to be restricted to lymphoid cells, could be demonstrated at protein level as well as by reverse transcription-PCR. DO:DM ratio correlated to CLIP:DR ratio, suggesting that, unlike in other antigen-presenting cells of the nonlymphoid cell type, both DO and DM mediate regulation of CLIP expression in AML blasts. We hypothesize that DR+/CLIP− AML blasts are able to present leukemia-specific antigens to CD4+ T helper cells initiating an effective and long-lasting antitumor response resulting in a prolonged disease-free survival.

B Cell Receptor-Mediated Internalization of Salmonella: A Novel Pathway for Autonomous B Cell Activation and Antibody Production

The present paradigm is that primary B cells are nonphagocytosing cells. In this study, we demonstrate that human primary B cells are able to internalize bacteria when the bacteria are recognized by the BCR. BCR-mediated internalization of Salmonella typhimurium results in B cell differentiation and secretion of anti-Salmonella Ab by the Salmonella-specific B cells. In addition, BCR-mediated internalization leads to efficient Ag delivery to the MHC class II Ag-loading compartments, even though Salmonella remains vital intracellularly in primary B cells. Consequently, BCR-mediated bacterial uptake induces efficient CD4+ T cell help, which boosts Salmonella-specific Ab production. BCR-mediated internalization of Salmonella by B cells is superior over extracellular Ag extraction to induce rapid and specific humoral immune responses and efficiently combat infection.

Langerhans Cells Favor Skin Flora Tolerance through Limited Presentation of Bacterial Antigens and Induction of Regulatory T Cells

The mechanisms preventing detrimental T-cell responses against commensal skin bacteria remain elusive. Using monocyte-derived and skin-derived dendritic cells (DCs), we demonstrate that epidermal Langerhans cells (LCs), the DCs in the most superficial layer of the skin, have a poor capacity to internalize bacteria because of low expression of FcγRIIa. Furthermore, LCs show deficiency in processing and major histocompatibility complex II (MHC-II)-restricted presentation of bacterial antigens, as a result of a decreased expression of molecules involved in these functionalities. The reduced capacity to take up, process, and present bacterial antigens cannot be restored by LC activation by ectopically expressed Toll-like receptors or by cytokines. Consequently, bacteria-primed LCs poorly restimulate antibacterial memory CD4(+) T cells and inefficiently induce bacteria-specific effector CD4(+) T cells from naive T cells; however, they initiate the development of regulatory Foxp3(+)CD4(+) T cells, which are able to suppress the proliferation of autologous bystander T cells specific for the same bacteria. In contrast, dermal DCs that reside in the deeper dermal layer of the skin efficiently present bacterial antigens and provoke robust antibacterial naive and memory CD4(+) T-cell responses. In conclusion, LCs form a unique DC subset that is adapted at multiple levels for the maintenance of tolerance to bacterial skin flora.

The Presence of Activated CD4+ T Cells Is Essential for the Formation of Colony-Forming Unit-Endothelial Cells by CD14+ Cells

The number of colony forming unit-endothelial cells (CFU-EC) in human peripheral blood was found to be a biological marker for several vascular diseases. In this study, the heterogeneous composition of immune cells in the CFU-ECs was investigated. We confirmed that monocytes are essential for the formation of CFU-ECs. Also, however, CD4+ T cells were found to be indispensable for the induction of CFU-EC colonies, mainly through cell-cell contact. By blocking or activating CD3 receptors on CD4+ T cells or blocking MHC class II molecules on monocytes, it was shown that TCR-MHCII interactions are required for induction of CFU-EC colonies. Because the supernatant from preactivated T cells could also induce colony formation from purified monocytes, the T cell support turned out to be cytokine mediated. Gene expression analysis of the endothelial-like colonies formed by CD14+ cells showed that colony formation is a proangiogenic differentiation and might reflect the ability of monocytes to facilitate vascularization. This in vitro study is the first to reveal the role of TCR-MHC class II interactions between T cells and monocytes and the subsequent inflammatory response as stimulus of monocytic properties that are associated with vascularization.

Antigen-Specific B Cells Reactivate an Effective Cytotoxic T Cell Response against Phagocytosed Salmonella through Cross-Presentation

Background The eradication of facultative intracellular bacterial pathogens, like Salmonella typhi, requires the concerted action of both the humoral immune response and the cytotoxic CD8+ T cell response. Dendritic cells (DCs) are considered to orchestrate the cytotoxic CD8+ T cell response via cross-presentation of bacterial antigens onto MHC class I molecules. Cross-presentation of Salmonella by DCs however, is accompanied by the induction of apoptosis in the DCs. Besides antibody production, B cells are required to clear Salmonella infection for other unknown reasons. Methodology/Principal Findings Here we show that Salmonella-specific B cells that phagocytose Salmonella upon BCR-ligation reactivate human memory CD8+ T cells via cross-presentation yielding a Salmonella-specific cytotoxic T cell response. The reactivation of CD8+ T cells is dependent on CD4+ T cell help. Unlike the DCs, B cell-mediated cross-presentation of Salmonella does not coincide with apoptosis. Conclusions/Significance B cells form a new player in the activation of the cytotoxic effector arm of the immune response and the generation of effective adaptive immunity in Salmonella infection.

CD5 costimulation induces stable Th17 development by promoting IL-23R expression and sustained STAT3 activation

IL-17-producing CD4(+) T helper (Th17) cells are important for immunity against extracellular pathogens and in autoimmune diseases. The factors that drive Th17 development in human remain a matter of debate. Here we show that, compared with classic CD28 costimulation, alternative costimulation via the CD5 or CD6 lymphocyte receptors forms a superior pathway for human Th17-priming. In the presence of the Th17-promoting cytokines IL-1β, IL-6, IL-23, and transforming growth factor-β (TGF-β), CD5 costimulation induces more Th17 cells that produce higher amounts of IL-17, which is preceded by prolonged activation of signal transducer and activator of transcription 3 (STAT3), a key regulator in Th17 differentiation, and enhanced levels of the IL-17-associated transcription factor retinoid-related orphan receptor-γt (ROR-γt). Strikingly, these Th17-promoting signals critically depend on CD5-induced elevation of IL-23 receptor (IL-23R) expression. The present data favor the novel concept that alternative costimulation via CD5, rather than classic costimulation via CD28, primes naive T cells for stable Th17 development through promoting the expression of IL-23R.