The WHO/IUIS Allergen Nomenclature Database (http://allergen.org) provides up‐to‐date expert‐reviewed data on newly discovered allergens and their unambiguous nomenclature to allergen researchers worldwide. This review discusses the 106 allergens that were accepted by the Allergen Nomenclature Sub‐Committee between 01/2019 and 03/2021. Information about protein family membership, patient cohorts, and assays used for allergen characterization is summarized. A first allergenic fungal triosephosphate isomerase, Asp t 36, was discovered in Aspergillus terreus. Plant allergens contained 1 contact, 38 respiratory, and 16 food allergens. Can s 4 from Indian hemp was identified as the first allergenic oxygen‐evolving enhancer protein 2 and Cic a 1 from chickpeas as the first allergenic group 4 late embryogenesis abundant protein. Among the animal allergens were 19 respiratory, 28 food, and 3 venom allergens. Important discoveries include Rap v 2, an allergenic paramyosin in molluscs, and Sal s 4 and Pan h 4, allergenic fish tropomyosins. Paramyosins and tropomyosins were previously known mainly as arthropod allergens. Collagens from barramundi, Lat c 6, and salmon, Sal s 6, were the first members from the collagen superfamily added to the database. In summary, the addition of 106 new allergens to the previously listed 930 allergens reflects the continuous linear growth of the allergen database. In addition, 17 newly described allergen sources were included.

Background: Birch pollen (BP) interacts with airway epithelial cells to cause allergic sensitization and allergy in predisposed individuals. However, the basic mechanisms underlying the clinical effects are poorly understood. Changes in gene expression and cytokine secretion in nasal mucosal cells upon BP exposure were determined in BP‐allergic and non‐allergic individuals.Methods: BP‐allergic (n = 11) and non‐allergic individuals (n = 12) participated in nasal provocations with saline and aqueous BP solution. Nasal scrapings and secretions were obtained at baseline and after BP provocation. Bulk RNA sequencing of the nasal scrapings was performed, and cytokines in nasal secretions were quantified.Results: After BP challenge, we identified 160 differentially expressed genes (DEGs) in the nasal scrapings of allergic individuals and 44 in non‐allergic individuals. DEGs encoding S100 proteins, keratins, small proline‐rich repeat proteins, and cytokines were predominantly identified, with proinflammatory cytokine transcripts being upregulated only in the allergic cohort. The top canonical pathways in allergic individuals included granulocyte and agranulocyte adhesion and diapedesis, wound healing, IL‐8 signaling, and IL‐17‐related pathways. Enriched pathways in allergic participants were associated with granulocyte chemotaxis, humoral cell responses, and IL‐10, IL‐4, and IL‐13 signaling and were absent in non‐allergic individuals. At baseline and after BP challenge, higher amounts of CCL17, CCL20, CCL26, IL‐7, IL‐16, and IL‐33 were detected in nasal secretions of allergic compared to non‐allergic individuals.Conclusion: Our results highlight the activation of important cellular signaling pathways specific to BP‐allergic individuals after BP exposure offering new perspectives for studying key players in BP allergy.

Pollen, in addition to allergens, comprise low molecular weight components (LMC) smaller than 3 kDa. Emerging evidence indicates the relevance of LMC in allergic immune responses. However, the interaction of birch pollen (BP)-derived LMC and epithelial cells has not been extensively studied. We investigated epithelial barrier modifications induced by exposure to BP LMC, using the human bronchial epithelial cell line 16HBE14o-. Epithelial cell monolayers were apically exposed to the major BP allergen Bet v 1, aqueous BP extract or BP-derived LMC. Barrier integrity after the treatments was monitored by measuring transepithelial electrical resistance at regular intervals and by using the xCELLigence Real-Time Cell Analysis system. The polarized release of cytokines 24 h following treatment was measured using a multiplex immunoassay. Epithelial barrier integrity was significantly enhanced upon exposure to BP LMC. Moreover, BP LMC induced the repair of papain-mediated epithelial barrier damage. The apical release of CCL5 and TNF-α was significantly reduced after exposure to BP LMC, while the basolateral release of IL-6 significantly increased. In conclusion, the results of our study demonstrate that BP-derived LMC modify the physical and immunological properties of bronchial epithelial cells and thus regulate airway epithelial barrier responses.

Plasmodium falciparum causes the most severe form of malaria in humans. The adhesion of the infected erythrocytes (IEs) to endothelial receptors (sequestration) and to uninfected erythrocytes (rosetting) are considered major elements in the pathogenesis of the disease. Both sequestration and rosetting appear to involve particular members of several IE variant surface antigens (VSAs) as ligands, interacting with multiple vascular host receptors, including the ABO blood group antigens. In this study, we subjected genetically distinct P. falciparum parasites to in vitro selection for increased IE adhesion to ABO antigens in the absence of potentially confounding receptors. The selection resulted in IEs that adhered stronger to pure ABO antigens, to erythrocytes, and to various human cell lines than their unselected counterparts. However, selection did not result in marked qualitative changes in transcript levels of the genes encoding the best-described VSA families, PfEMP1 and RIFIN. Rather, overall transcription of both gene families tended to decline following selection. Furthermore, selection-induced increases in the adhesion to ABO occurred in the absence of marked changes in immune IgG recognition of IE surface antigens, generally assumed to target mainly VSAs. Our study sheds new light on our understanding of the processes and molecules involved in IE sequestration and rosetting.

Background: Basophils are important mediators in the pathobiology of atopic diseases, yet the heterogeneity of basophils within the perinatal environment remains incompletely understood. In our study, we aimed to perform comprehensive profiling of paired maternal and cord blood basophils using a single‐cell omics approach to look into their distinct transcriptional signatures. Methods: Basophils were isolated from four paired maternal‐cord blood samples at the time of delivery, including one mother who delivered monozygotic twins. Basophil characterization of maternal blood (MB) and cord blood (CB) was analyzed in flow cytometry. Single cell RNA sequencing (scRNA‐seq) was performed to further examine the basophils composition and heterogeneity in MB and CB. Results: We observed that CB basophils have lower expression of FCER1A, and no cell‐bound or circulating IgE levels as compared to MB. Our scRNA‐seq data show that MB and CB basophils are different in both transcriptomic and functional profiles. CB basophils exhibit greater heterogeneity than MB. Low interindividual variability between twin CB basophil samples confirmed that the transcriptomic difference between MB and CB basophils is biologically meaningful. Trajectory pseudotime analysis revealed that CB basophils have an earlier pseudotime, potentially indicating a more naïve state. In addition, we demonstrated that CB basophils exhibit distinct functional capacities. Conclusion: Our data identified protein and gene signatures in MB and CB basophils. We demonstrated that CB has greater heterogeneity than MB basophils, thereby highlighting the relevance of single cell profiling of basophils in the context of the maternal‐fetal interface.