Estimation of serum and tissue level of interleukin‐15 (IL‐15) and IL‐15 receptor alpha (IL‐15Rα) in mycosis fungoides before and after phototherapy: An interventional cohort study

Background Mycosis fungoides (MF) is a chronic, highly recurrent cutaneous T‐cell lymphoma, whose pathogenesis has not yet been fully elucidated. Interleukin‐15 was previously highlighted as a viability factor for cutaneous T‐cell lymphoma with previous studies shedding light on its role in pathogenesis of MF and its plausibility as a potential therapeutic target. Objective This study was conducted to evaluate serum and tissue expression of IL‐15 and IL‐15Rα in early cases of MF (IA, IB, IIA) at baseline and following phototherapy. Materials and Methods Fourteen early MF cases were recruited. Samples were withdrawn prior to starting phototherapy treatment and following near complete clearance of the biopsied lesion or after a maximum of 36 sessions of phototherapy. Samples were assessed for change in expression of IL‐15 and IL‐15 Rα levels following treatment, whose levels were compared to healthy controls. Results Serum and tissue levels of IL‐15 and IL‐15Rα in early MF cases were significantly higher at baseline than their levels following phototherapy treatment and higher than healthy controls. However, they dropped significantly following treatment with no statistical difference between treated cases and controls, apart from serum IL‐15Rα that remained significantly elevated than controls. Conclusion Interleukin‐15 and its receptor alpha appear to contribute to the pathogenesis of MF, being significantly elevated than healthy controls, which were normalized following phototherapy treatment, apart from serum IL‐15Rα, which remained elevated. Controlling IL‐15/IL‐15Rα expression is a newly proposed mechanism of action of phototherapy in MF.