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A growing body of clinical and experimental evidence indicates that immune checkpoint blockade enhances patient susceptibility to hypersensitivity reactions to co-administered medications. In this study, we utilized an in vitro T-cell priming assay to demonstrate one of the mechanistic hypotheses on how this occurs; through lowering of the threshold in patients to elicit aberrant T-cell responses. We outline the dependency of de novo T-cell priming responses to drug-associated antigens on dose at initial exposure. Findings support the aforementioned hypothesis and offer an experimental representation of fundamental parameters at play in hypersensitivity reactions to low molecular weight compounds. [ABSTRACT FROM AUTHOR]

ABSTRACT Biological agents are widely used across medicine, including for immune‐mediated skin conditions such as psoriasis and atopic dermatitis. When used to treat a relevant pathological process, they demonstrate impressive efficacy and credible safety, helping to achieve remission and improved function and quality of life. However, with their expanded use, awareness and understanding of adverse reactions to biologicals have also increased. Herein, we discuss the pathomechanism of adverse reactions to biological agents used to treat skin conditions and apply these to Pichler's classification system. This classification differentiates five distinct types, namely overstimulation (type α), hypersensitivity or immunogenicity (β), immunodeviation (γ), cross‐reactivity (δ) and nonimmunologic adverse reactions (ε). This classification covers most types of adverse reactions associated with use of biological agents and could be used to better understand the reaction pathogenesis and manage the clinical features of biological adverse effects. [ABSTRACT FROM AUTHOR]

Summary: Immune responses to primary COVID‐19 vaccination were investigated in 58 patients with follicular lymphoma (FL) as part of the PETReA trial of frontline therapy (EudraCT 2016–004010‐10). COVID‐19 vaccines (BNT162b2 or ChAdOx1) were administered before, during or after cytoreductive treatment comprising rituximab (depletes B cells) and either bendamustine (depletes CD4+ T cells) or cyclophosphamide‐based chemotherapy. Blood samples obtained after vaccine doses 1 and 2 (V1, V2) were analysed for antibodies and T cells reactive to the SARS‐CoV‐2 spike protein using the Abbott Architect and interferon‐gamma ELISpot assays respectively. Compared to 149 healthy controls, patients with FL exhibited lower antibody but preserved T‐cell responses. Within the FL cohort, multivariable analysis identified low pre‐treatment serum IgA levels and V2 administration during induction or maintenance treatment as independent determinants of lower antibody and higher T‐cell responses, and bendamustine and high/intermediate FLIPI‐2 score as additional determinants of a lower antibody response. Several clinical scenarios were identified where dichotomous immune responses were estimated with >95% confidence based on combinations of predictive variables. In conclusion, the immunogenicity of COVID‐19 vaccines in FL patients is influenced by multiple disease‐ and treatment‐related factors, among which B‐cell depletion showed differential effects on antibody and T‐cell responses. [ABSTRACT FROM AUTHOR]

Immunotherapy advances have been hindered by difficulties in tracking the behaviors of lymphocytes after antigen signaling. Here, we assessed the behavior of T cells active within tumors through the development of the antigen receptor signaling reporter (AgRSR) mouse, fate-mapping lymphocytes responding to antigens at specific times and locations. Contrary to reports describing the ready egress of T cells out of the tumor, we find that intratumoral antigen signaling traps CD8+ T cells in the tumor. These clonal populations expand and become increasingly exhausted over time. By contrast, antigen-signaled regulatory T cell (Treg) clonal populations readily recirculate out of the tumor. Consequently, intratumoral antigen signaling acts as a gatekeeper to compartmentalize CD8+ T cell responses, even within the same clonotype, thus enabling exhausted T cells to remain confined to a specific tumor tissue site. Editor's summary: An understanding of how T cells behave after antigen signaling is critical to improving immunotherapies. Takahashi et al. developed the antigen receptor signaling reporter (AgRSR) mice to fate-map T cells responding to antigen signals. In tumors, they showed that antigen engagement caused clonally expanded CD8 T cells to be retained within tumors, resulting in T cell exhaustion. Whereas antigen engagement of regulatory T cells (Tregs) within tumors similarly induced clonal expansion, Tregs were able to recirculate. These results provide insight into T cell behaviors that may limit antitumor responses and introduce a system for tracking adaptive immunity. —Christiana Fogg [ABSTRACT FROM AUTHOR]

Background: Exposure to nonsteroidal anti‐inflammatory drugs (NSAIDs) such as ibuprofen (IBU) and naproxen (NAP) is associated with idiosyncratic drug‐induced liver injury (DILI). Carboxylate bioactivation into reactive metabolites (e.g., acyl glucuronides, AG) and resulting T‐cell activation is hypothesized as causal for this adverse event. However, conclusive evidence supporting this is lacking. Methods: In this work, we identify CD4+ and CD8+ T‐cell hepatic infiltration in a biopsy from an IBU DILI patient. Lymphocyte transformation test and IFN‐γ ELIspot, conducted on peripheral blood mononuclear cells (PBMCs) of patients with NAP‐DILI, were used to explore drug‐specific T‐cell activation. T‐cell clones (TCC) were generated and tested for drug specificity, phenotype/function, and pathways of T‐cell activation. Cells were exposed to NAP, its oxidative metabolite 6‐O‐desmethyl NAP (DM‐NAP), its AG or synthesized NAP‐AG human‐serum albumin adducts (NAP‐AG adduct). Results: CD4+ and CD8+ T‐cells from patients expressing a range of different Vβ receptors were stimulated to proliferate and secrete IFN‐γ and IL‐22 when exposed to DM‐NAP, but not NAP, NAP‐AG or the NAP‐AG adduct. Activation of the CD4+ TCC was HLA‐DQ‐restricted and dependent on antigen presenting cells (APC); most TCC were activated with DM‐NAP‐pulsed APC, while fixation of APC blocked the T‐cell response. Cross‐reactivity was not observed with structurally‐related drugs. Conclusion: Our results confirm hepatic T‐cell infiltrations in NSAID‐induced DILI, and show a T‐cell memory response toward DM‐NAP indicating an immune‐mediated basis for the adverse event. Whilst bioactivation at the carboxylate group is widely hypothesized to be pathogenic for NSAID associated DILI, we found no evidence of this with NAP. [ABSTRACT FROM AUTHOR]

In vitro preclinical drug-induced liver injury (DILI) risk assessment relies largely on the use of hepatocytes to measure drug-specific changes in cell function or viability. Unfortunately, this does not provide indications toward the immunogenicity of drugs and/or the likelihood of idiosyncratic reactions in the clinic. This is because the molecular initiating event in immune DILI is an interaction of the drug-derived antigen with MHC proteins and the T-cell receptor. This study utilized immune cells from drug-naïve donors, recently established immune cell coculture systems and blinded compounds with and without DILI liabilities to determine whether these new methods offer an improvement over established assessment methods for the prediction of immune-mediated DILI. Ten blinded test compounds (6 with known DILI liabilities; 4 with lower DILI liabilities) and 5 training compounds, with known T-cell-mediated immune reactions in patients, were investigated. Naïve T-cells were activated with 4/5 of the training compounds (nitroso sulfamethoxazole, vancomycin, Bandrowski's base, and carbamazepine) and clones derived from the priming assays were activated with drug in a dose-dependent manner. The test compounds with DILI liabilities did not stimulate T-cell proliferative responses during dendritic cell-T-cell coculture; however, CD4+ clones displaying reactivity were detected toward 2 compounds (ciprofloxacin and erythromycin) with known liabilities. Drug-responsive T-cells were not detected with the compounds with lower DILI liabilities. This study provides compelling evidence that assessment of intrinsic drug immunogenicity, although complex, can provide valuable information regarding immune liabilities of some compounds prior to clinical studies or when immune reactions are observed in patients. [ABSTRACT FROM AUTHOR]

Epidermal growth factor receptor inhibitors (EGFRIs) are widely used to treat various types of malignancies. One of the common adverse reactions is cutaneous toxicity, mostly presenting as acneiform eruptions, paronychia and xerosis. Erosive pustular dermatosis of the scalp (EPDS) is a rare cutaneous adverse reaction that develops during treatment with EGFRIs. The pathogenesis of EGFRI-induced EPDS is poorly understood. Here we present three cases of EPDS induced by EGFRIs. The proteins LTA4H (leukotriene A-4 hydrolase), METAP1 (methionine aminopeptidase 1), BID (BH3-interacting domain death agonist), SMAD1 (mothers against decapentaplegic homologue), PRKRA (interferon-inducible double-stranded RNA-dependent protein kinase activator A), YES1 (tyrosine-protein kinase Yes) and EGFL7 (epidermal growth factor-like protein 7) were significantly upregulated in EGFRI-stimulated peripheral blood mononuclear cell cultures, and validated in the lesions. All of the proteins colocalized with CD4+ and CD8+ T-cell expression. Next-generation-based human leucocyte antigen (HLA) typing showed all patients carried HLA-C*15:02, and modelling studies showed that afatinib and erlotinib bound well within the E/F binding pockets of HLA-C*15:02. Moreover, T cells were preferentially activated by EGFRIs in individuals carrying HLA-C*15:02. The case series revealed that EGFRI-induced EPDS may be mediated by drug-specific T cells. [ABSTRACT FROM AUTHOR]