Fig 1: A single nucleotide polymorphism linked to immunodeficiency blocks binding of IL23-TMR and P630-TMR.a Left: Crystal structure of N-terminal domains 1–3 of IL23R (orange) in complex with IL-23 (IL23p19 = blue, IL12p40 = green) and the N-terminal domain of IL12Rß1 (PDB: 6WDQ13). Right: The interface between IL23R and IL23p19 with C115 coloured cyan. b The phospho-STAT3 signal generated when cells expressing different constructs were treated with 5 nM IL-23. Data are mean ± SEM from five or six (untagged) or three (NanoLuc tagged) independent experiments conducted in triplicate. For the IL23R + IL12Rß1 data set, one outlier (11108.7) was detected using the Grubbs test (with alpha = 0.001) and removed from the statistical analysis. Statistical significance of the C115Y mutation on the alphaLISA data was assessed using a 2-way ANOVA with Tukey’s multiple comparison test. ***p < 0.001. The p value for the comparison of NL tagged construct response was 0.0001 and the p value for the comparison of untagged receptor was 0.951. c Luminescence signal measured when IL12Rß1 was expressed with either NL-IL23R or the C115Y mutant. Data are mean ± SEM generated from the mean luminescence values of seven (C115Y) or eight independent experiments performed in pentuplicate. d The proportion of luminescence from c that emanated from extracellular protein (as defined by the reduction in luminescence after treatment with 60 µM NanoLuc extracellular inhibitor). Data are mean ± SEM generated from the mean luminescence values of five (C115Y) or six independent experiments performed in triplicate. e The BRET ratio generated from HaloTag-618 labelled cells expressing NL tagged wildtype or C115Y IL23R with HT-IL12Rß1 or unlabelled IL12Rß1. Data are mean ± SEM generated from the mean BRET values of three independent experiments performed in pentuplicate. Statistical significance of differences in mean values shown in c–e were measured using a 2-sided, non-paired t test with ** indicating a p value of <0.005 and *** indicating a p value of <0.0005. The p values for the results shown in c, d and e were p = 0.148, 0.0005 and 0.0013 respectively. Source data are provided as a Source Data file.