Role of T cells in non-immediate drug allergy reactions

Advances and highlights in T and B cell responses to drug antigens

The immunological mechanisms involved in drug hypersensitivity reactions (DHRs) are complex, and despite important advances, multiple aspects remain poorly understood. These not fully known aspects are mainly related to the factors that drive towards either a tolerant or a hypersensitivity response and specifically regarding the role of B and T cells. In this review, we focus on recent findings on this knowledge area within the last 2 years. We highlight new evidences of covalent and non-covalent interactions of drug antigen with proteins, as well as the very first characterization of naturally processed flucloxacillin-haptenated human leukocyte antigen (HLA) ligands. Moreover, we have analysed new insights into the identification of risk factors associated with the development of DHRs, such as the role of oxidative metabolism of drugs in the activation of the immune system and the discovery of new associations between DHRs and HLA variants. Finally, evidence of IgG-mediated anaphylaxis in humans and the involvement of specific subpopulations of effector cells associated with different clinical entities are also topics explored in this review. All these recent findings are relevant for the underlying pathology mechanisms and advance the field towards a more precise diagnosis, management and treatment approach for DHRs.

SARS-CoV-2, COVID-19, skin and immunology - What do we know so far?

The pandemic condition coronavirus disease (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can take asymptomatic, mild, moderate, and severe courses. COVID-19 affects primarily the respiratory airways leading to dry cough, fever, myalgia, headache, fatigue, and diarrhea and can end up in interstitial pneumonia and severe respiratory failure. Reports about the manifestation of various skin lesions and lesions of the vascular system in some subgroups of SARS-CoV-2-positive patients as such features outside the respiratory sphere, are rapidly emerging. Vesicular, urticarial, and maculopapular eruptions and livedo, necrosis, and other vasculitis forms have been reported most frequently in association with SARS-CoV-2 infection. In order to update information gained, we provide a systematic overview of the skin lesions described in COVID-19 patients, discuss potential causative factors, and describe differential diagnostic evaluations. Moreover, we summarize current knowledge about immunologic, clinical, and histologic features of virus- and drug-induced lesions of the skin and changes to the vascular system in order to transfer this knowledge to potential mechanisms induced by SARS-CoV-2.