Does the antimicrobial peptide, granulysin, play a role in decreasing the incidence of secondary bacterial infection in psoriasis?

Background Although the skin is constantly challenged by microbes, it is rarely infected. Cutaneous production of antimicrobial peptides is a primary system for protection. Patients with psoriasis, a chronic, hyperproliferative, and noninfectious skin disease, suffer fewer cutaneous infections than would be expected. Granulysin is a recently identified antimicrobial protein expressed in cytotoxic T cells, natural killer cells, and natural killer T cells. It has been shown that granulysin contributes toward the defense mechanisms against mycobacterial infection. Objective To estimate the tissue level of granulysin in psoriatic patients versus controls aiming to prove its possible role as antimicrobial peptide in preventing secondary bacterial infection in psoriasis. Patients and methods This study included 15 patients with psoriasis and 15 healthy volunteers as controls. Five millimeter punch skin biopsies were taken from all patients and controls and assessed for granulysin by enzyme-linked immunosorbent assay technique. Results Granulysin level in psoriatic patients was significantly higher compared with that of normal controls (P = 0.001). Correlation between granulysin level and Psoriasis Area and Severity Index score showed a statistically significant positive correlation (P = 0.001). Conclusion High tissue level of granulysin in psoriatic patients may participate in the pathogenesis of psoriasis and provide an explanation for the relative immunity of psoriatic plaques against both gram-positive and gram-negative bacterial infections.