Neutrophils from burn patients suppress the beta‐defensin production by human epidermal keratinocytes

Recently, we have isolated immunosuppressive neutrophils (PMN‐II) from patients with severe thermal injuries. PMN‐II play a role on the increased susceptibility of burn hosts to various infections. Since antimicrobial peptides have been described as important effector molecules on host antimicrobial innate immunities, in the present study, the influence of PMN‐II on the beta‐defensins (BD) production by human keratinocytes has been studied. Normal human epidermal keratinocytes (NHEK: 5×10 5 cells, Lonza) were cultured with neutrophils (1×10 5 cells, upper chamber), isolated from burn patients or normal volunteers, in dual‐chamber transwells. Culture fluids harvested 24 hrs after cultivation were assayed for BD by ELISA. Also, these culture fluids were analyzed for their antimicrobial activities by a standard colony counting method using Pseudomonas aeruginosa . PMN from burn patients were confirmed as PMN‐II by their cytokine/chemokine producing profiles. The production of BD2 and BD3 by NHEK was suppressed by PMN from burn patients. The culture fluids of NHEK transwell‐cultured with burn patient PMN showed decreased antimicrobial activities, as compared with controls (culture fluids of NHEK transwell‐cultured with healthy PMN). PMN isolated from peripheral blood of burn patients were confirmed as PMN‐II, because these cells produced IL‐10 and CCL2, but not IL‐12 and CCL3. These results indicate that PMN‐II appeared in association with burn injury contribute to the decreased production of BD in thermally injured patients. (Supported by SHC NA #8840.)