Overexpression of the high-affinity Fc gamma receptor (CD64) is associatedwith leukocyte dysfunction in sepsis

The morbidity and mortality from sepsis and multiple organ dysfunction synd rome (MODS) continues to be high. An increase in Fc gamma RI+ (CD64+) monoc ytes was demonstrated in septic patients, and an association between cell n umber, their secretory activity, and poor outcome has been described. In th e present investigation further characterization of CD64+ leukocytes has be en attempted. The study was aimed at examining the phagocytic activity (PA) and reactive oxygen species (ROS) production by monocytes (Mo) and neutrop hils (Neu) in sepsis and sepsis-induced acute respiratory distress syndrome (ARDS) related to the pattern of CD64 expression. Twenty-three post-trauma tic or post-operative male and female patients with sepsis were enrolled. T he control group consisted of 10 healthy volunteers. Arterial blood samples were taken during the septic episode for flow cytometric analysis of surfa ce leukocyte antigens, phagocytosis, and ROS production. CD64 expression on Mo and Neu was markedly increased in septic patients (P = 0.029 and P = 0. 0005), and even more in sepsis with ARDS (P = 0.011). In healthy individual s, PA of CD64+ Neu was higher, than of CD64- cells (P = 0.021). In septic p atients, decreased PA was detected in CD64+ Mo and Neu (P = 0.013 and P = 0 .040, respectively). CD64+ Neu of patients in ARDS exhibited the most promi nent PA depression (P = 0.048). ROS production in non-separated Mo and Neu was increased in sepsis (P = 0.026 and P = 0.004, respectively). In healthy individuals CD64+ Neu and stimulated CD64+ Mo demonstrated increased ROS s ynthesis compared to matched CD64- cells (P = 0.001 and P = 0.042, respecti vely). Although ROS production by CD64+ leukocytes in sepsis was also incre ased compared to CD64- cells, significantly less ROS was generated compared to healthy subjects (P = 0.021). In conclusion, overexpression of CD64 on blood Mo and Neu from patients with sepsis and ARDS is associated with depr essed PA and decreased oxidative response.