Human cells homozygous for rare loss-of-expression (LOE) TYK2 alleles have impaired, but not abolished, cellular responses to IFN-α/β (underlying viral diseases in the patients) and to IL-12 and IL-23 (underlying mycobacterial diseases). Cells homozygous for the common P1104A TYK2 allele have selectively impaired responses to IL-23 (underlying isolated mycobacterial disease). We report three new forms of TYK2 deficiency in six patients from five families homozygous for rare TYK2 alleles (R864C, G996R, G634E, or G1010D) or compound heterozygous for P1104A and a rare allele (A928V). All these missense alleles encode detectable proteins. The R864C and G1010D alleles are hypomorphic and loss-of-function (LOF), respectively, across signaling pathways. By contrast, hypomorphic G996R, G634E, and A928V mutations selectively impair responses to IL-23, like P1104A. Impairment of the IL-23–dependent induction of IFN-γ is the only mechanism of mycobacterial disease common to patients with complete TYK2 deficiency with or without TYK2 expression, partial TYK2 deficiency across signaling pathways, or rare or common partial TYK2 deficiency specific for IL-23 signaling.

Background: Genetic deficiencies of immune system, referred to as inborn errors of immunity (IEI), serve as a valuable model to study human immune responses. In a multicenter prospective cohort, we evaluated the outcome of SARS‐CoV‐2 infection among IEI subjects and analyzed genetic and immune characteristics that determine adverse COVID‐19 outcomes.Methods: We studied 34 IEI patients (19M/15F, 12 [min: 0.6‐max: 43] years) from six centers. We diagnosed COVID‐19 infection by finding a positive SARS‐CoV‐2 PCR test (n = 25) and/or a lung tomography scoring (CORADS) ≥4 (n = 9). We recorded clinical and laboratory findings prospectively, fitted survival curves, and calculated fatality rates for the entire group and each IEI subclass.Results: Nineteen patients had combined immune deficiency (CID), six with predominantly antibody deficiency (PAD), six immune dysregulation (ID), two innate immune defects, and one in the autoinflammatory class. Overall, 23.5% of cases died, with disproportionate fatality rates among different IEI categories. PAD group had a relatively favorable outcome at any age, but CIDs and IDs were particularly vulnerable. At admission, presence of dyspnea was an independent risk for COVID‐related death (OR: 2.630, 95% CI; 1.198–5.776, p < .001). Concerning predictive roles of laboratory markers at admission, deceased subjects compared to survived had significantly higher CRP, procalcitonin, Troponin‐T, ferritin, and total‐lung‐score (p = .020, p = .003, p = .014, p = .013, p = .020; respectively), and lower absolute lymphocyte count, albumin, and trough IgG (p = .012, p = .022, p = .011; respectively).Conclusion: Our data disclose a highly vulnerable IEI subgroup particularly disadvantaged for COVID‐19 despite their youth. Future studies should address this vulnerability and consider giving priority to these subjects in SARS‐Cov‐2 therapy trials.

Background: Antigen‐specific memory B cells play a key role in the induction of desensitization and remission to food allergens in oral immunotherapy and in the development of natural tolerance (NT). Here, we characterized milk allergen Bos d 9‐specific B cells in oral allergen‐specific immunotherapy (OIT) and in children spontaneously outgrowing cow's milk allergy (CMA) due to NT.Methods: Samples from children with CMA who received oral OIT (before, during, and after), children who naturally outgrew CMA (NT), and healthy individuals were received from Stanford biobank. Bos d 9‐specific B cells were isolated by flow cytometry and RNA‐sequencing was performed. Protein profile of Bos d 9‐specific B cells was analyzed by proximity extension assay.Results: Increased frequencies of circulating milk allergen Bos d 9‐specific B cells were observed after OIT and NT. Milk‐desensitized subjects showed the partial acquisition of phenotypic features of remission, suggesting that desensitization is an earlier stage of remission. Within these most significantly expressed genes, IL10RA and TGFB3 were highly expressed in desensitized OIT patients. In both the remission and desensitized groups, B cell activation‐, Breg cells‐, BCR‐signaling‐, and differentiation‐related genes were upregulated. In NT, pathways associated with innate immunity characteristics, development of marginal zone B cells, and a more established suppressor function of B cells prevail that may play a role in long‐term tolerance. The analyses of immunoglobulin heavy chain genes in specific B cells demonstrated that IgG2 in desensitization, IgG1, IgA1, IgA2, IgG4, and IgD in remission, and IgD in NT were predominating. Secreted proteins from allergen‐specific B cells revealed higher levels of regulatory cytokines, IL‐10, and TGF‐β after OIT and NT.Conclusion: Allergen‐specific B cells are essential elements in regulating food allergy towards remission in OIT‐received and naturally resolved individuals.