Saini C, et al. - Given that 30–40% leprosy patients develop type 1 reactions (T1R), an inflammatory condition of local skin patches, during the course of MDT, and a crucial role of IL-17A and IL-17F in regulating skin inflammation by neutrophils is known, researchers performed this inquiry, wherein they used flow cytometry and qPCR to evaluate 18 of each T1R and Non-reactions (NR) patients. Relative to NR leprosy patients, significantly high CD3⁺CD4⁺ gated IL-17A⁺IL-17F⁺ cells were detected in T1R in both MLSA stimulated PBMCs and skin lesions. Significant links of CXCL6, CXCL5, CCL20, CCL7, MMP13 and IL-17RB expression with IL-17A and IL-17F expression, neutrophils and monocyte markers, respectively, were revealed in hierarchical clustering analysis of gene expression. A different phenotype of Th17 was characterized by the presence of inflammation in lesions of T1R. This phenotype generated double positive IL-17A⁺IL17F⁺ as well as contributed IL-17 generating neutrophils, and therefore, displayed potential utility for monitoring, diagnosis and treatment response prior to reactions episodes.