Expression of granulysin and FOXP3 in cutaneous T cell lymphoma and Sézary syndrome

Background: Multiple complex pathways are operable in the evolution of cutaneous T cell lymphomas (CTCLs). These pathways involve interaction between neoplastic T cells and cells of the immune system (especially dendritic cells and the non-malignant T cells). Granulysin is a proinflammatory antimicrobial peptide which has an immune alarmin function, activating dendritic cells, as well as an active role in tumor immunology and prognosis. FOXP3+ regulatory T cells Tregs are an important player in the immune system. Much controversy is found in the literature about the role of Tregs in CTCL. Aim: The present study aimed to investigate the expression of granulysin and FOXP3 in mycosis fungoides (MF), its precursor lesion large plaque parapsoriasis and its leukemic form Sézary syndrome (SS). Materials and Methods: Immunohistochemical expression of granulysin and FOXP3 were assessed in lesional skin biopsies taken from 58 patients (4 large plaque parapsoriasis, 48 MF and 6 SS). Results: Granulysin positivity was cytoplasmic and higher in MF than in parapsoriasis en plaque and higher in the more advanced stages of MF (p<0.001). All groups showed significant differences between each other except between MF tumor stage and SS. FOXP3 positivity was nuclear and higher in early stage MF (plaque and patch stages) than in tumor stages and SS (p<0.001). However the FOXP3 count was lower in parapsoriasis en plaque than in other stages of MF. All the groups showed significant differences between each other except between parapsoriasis and SS and between patch and plaque stages of MF. Conclusions: The present study supports a role for granulysin in MF progression and proposes a novel hypothesis about the effect of FOXP3 +veTregs in the suppression of the activity of the neoplastic cells in MF.