Figure 7. AS-associated SNPs at the TYK2 locus do not alter TYK2 expression, but correlate with altered Th1 frequency and AS disease progression.

qPCR was used to assess whole-blood TYK2 expression in a cohort of 47 healthy controls (HC), 76 ankylosing spondylitis patients (AS), and 21 rheumatoid arthritis patients (RA) by patient type (A) and rs35164067 (B) and rs12720356 (C) genotypes. (D) TYK2 expression in peripheral joint synovial biopsies measured by qPCR. PrimeFlow was used to detect TYK2 mRNA by flow cytometry. (E) Representative histograms showing TYK2 mRNA expression in selected cell populations. White histograms represent FMO controls, gray histograms represent TYK2-stained cells. Values under cell populations are the respective MFIs of TYK2. (F) TYK2 MFI in CD4⁺ T cells by patient group. (G) AS/RA/HC subjects were pooled to assess TYK2 expression by rs12720356 genotype. (H) PBMCs from the same cohort were stimulated with PMA/ionomycin for IL-17A and IFN-γ detection by flow cytometry. AS, RA, and HC pooled and data stratified by rs12720356. (I) Frequency chart of rs12720356 genotype assessed in a separate cohort of AS patients with progressing (n = 84) or nonprogressing (n = 79) disease based on mSASSS scores. qPCR analysis in A–C was normalized to HPRT expression and to GAPDH in D. A and B, 1-way ANOVA with Tukey post hoc test; C, D, and H, Mann-Whitney test; I, Fisher’s exact test. *P < 0.05, **P < 0.01.