Regulatory T cell features in chronic granulomatous disease

Summary Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by mutations in any of the genes encoding the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system, responsible for the production of reactive oxygen species (ROS). CGD is marked by invasive bacterial and fungal infections and by autoinflammation/autoimmunity, of which the exact pathophysiology remains elusive. Contributing factors include decreased neutrophil apoptosis, impaired apoptotic neutrophil clearance, increased proinflammatory protein expression and reduced ROS‐mediated inflammasome dampening. We have explored a fundamentally different potential mechanism: it has been reported that macrophage‐mediated induction of regulatory T cells (T regs ) depends on ROS production. We have investigated whether numerical or functional deficiencies exist in T regs of CGD patients. As the prevalence of autoinflammation/autoimmunity differs between CGD subtypes, we have also investigated T regs from gp91 phox ‐, p47 phox ‐ and p40 phox ‐deficient CGD patients separately. Results show that T reg numbers and suppressive capacities are not different in CGD patients compared to healthy controls, with the exception that in gp91 phox ‐deficiency effector T reg (eT reg ) numbers are decreased. Expression of T reg markers CD25, inducible T cell co‐stimulator (ICOS), Helios, cytotoxic T lymphocyte antigen 4 (CTLA‐4) and glucocorticoid‐induced tumor necrosis factor receptor (GITR) did not provide any clue for differences in T reg functionality or activation state. No correlation was seen between eT reg numbers and patients' clinical phenotype. To conclude, the only difference between T regs from CGD patients and healthy controls is a decrease in circulating eT regs in gp91 phox ‐deficiency. In terms of autoinflammation/autoimmunity, this group is the most affected. However, upon culture, patient‐derived T regs showed a normal phenotype and normal functional suppressor activity. No other findings pointed towards a role for T regs in CGD‐related autoinflammation/autoimmunity.