evaluation of il17 producing memory regulatory and effector t cells expressing cd26 molecule in patients with psoriasis

Memory regulatory t cells (tregs) has been demonstrated to produce il17 in psoriasis. forkhead box p3 (foxp3) has been demonstrated not to be reliable marker to evaluate treg cells. effector cd4^+t cells also express foxp3 after activation. human t helper17 cells (th17) express high level of surface cd26, while regulatory t cells are cd26 negative or low and this phenotype is stable even after activation of treg cells. in this study, we aimed to analyze il17 producing treg cells using cd26. memory t cells were isolated from 10 patients with psoriasis and 10 controls. ex vivo stimulated il17 producing regulatory (forkhead box p3 (foxp3)^+cd25^+cd26/low) and effector (foxp3^+cd25^+cd26hi) memory t cells were analyzed by flow cytometry. il23, il6, tnfα, tgfβ and il17 cytokine levels were also evaluated. no significant difference in il17^+memory regulatory t cells was seen between patients and controls (p=0.19). a significant decrease in the percentage of il17 producing cd26hi effector memory t cells was observed in patients (p=0.04). however, the percentage of these cells was not different between patients with mild or severe form of psoriasis compared to controls (p=0.13). we could not find any significant difference regarding il23, il6, tnfα, tgfβ and il17 cytokine levels in plasma and cell culture supernatant samples between patients and controls. taken together, our results showed a reduced il17 producing effector memory cd26hi t cells in patients with psoriasis compared to controls. however, il17 producing memory regulatory cd4^+t cells of patients showed no significant difference from that of controls.