TYK2 and acute lymphoblastic leukemia: None of the TYK2 variants were found in the five B-cell lines analysed, whereas seven were detected in B-ALL samples: located in exon 9 (JH4), rs150601734 that causes arginine-to-histidine substitution (p.Arg425His) (TYK2 R425H) in one patient; in exon 15 (JH2), rs12720356 (p.Ile684Ser) (TYK2 I684S) in eleven patients (17.74%), and rs55882956 (p.Arg703Trp) (TYK2 R703W) in one case; in exon 18 (JH2), rs144995884 (p.Arg832Trp) (TYK2 R832W) was detected in one patient.