Human monocytes produce interferon-gamma upon stimulation with LPS

Representing a crucial T-helper 1 cytokine, IFN-gamma acts as an important bridge between innate and adaptive immunity and is involved in many acute and chronic pathologic states, such as autoimmune diseases and solid organ transplant rejection. At present, debate still prevails about the ability of human monocytes to produce IFN-gamma. We aimed to investigate whether human monocytes possess the capacity to produce IFN-gamma at mRNA and protein level. Using real time PCR, flow cytometric analysis and ELISA, we investigated the capacity of freshly isolated CD14+ monocytes of healthy individuals and kidney transplant recipients to produce IFN-gamma after stimulation with IFN-gamma and LPS or LPS alone. We observed increased IFN-gamma mRNA levels in CD14+ monocytes after stimulation as compared to the unstimulated controls in both populations. In addition, stimulation with IFN-gamma and LPS or LPS alone led to a significant increase in the percentage of CD14+ monocytes producing TNF-alpha and IFN-gamma at protein level (p < 0.05). A trend towards increased secreted IFN-gamma production in supernatants was also observed after LPS stimulation using ELISA. We conclude that human monocytes from healthy individuals and kidney transplant recipients possess the capacity to produce IFN-gamma. (C) 2014 Elsevier Ltd. All rights reserved.