Increased intracellular and extracellular oxidant production in phagocytes of rheumatic patients treated with biological therapy – whole blood quantification

Infectious complications, resulting from reduced activity of immune cells, are the most severe and common adverse effects of biological therapy. This study analyzed the effect of biological therapy on blood phagocytes, focusing on the formation of reactive oxygen species (ROS), an important factor in the defence against invading pathogens. Intra- and extracellular ROS production were recorded separately, on the basis of luminol and isoluminol chemiluminescence in patients treated with antibodies against tumor necrosis factor-α or against interleukin-6 receptor. In comparison to healthy donors or to rheumatic patients treated with classical immunosuppressive drugs, biological therapy increased ROS formation in both compartments. This indicates that the anti-microbial activity of blood phagocytes was not reduced by TNFα- or IL-6-neutralizing therapy, at least in terms of ROS. The method presented does not require blood fractionation, which could modify activity of phagocytes and cause loss of some subpopulations of these cells. The technique is simple, requires microliter volumes of blood and is thus well applicable to clinical studies.