Pseudomonas aeruginosa (PA) pneumonia is a refractory, even lethal complication in immunosuppressive individuals and immune disturbances may promote the pathological process. We aimed to investigate the regulatory T (Treg) cell activity in an immunosuppressive mice model of PA pneumonia by estimating levels of main transcription factor and the main effector of Treg cells, i.e., Forkhead box protein 3 (FOXP3) and interleukine-10 (IL-10). Seventy-two BALB/c mice were divided into four groups randomly: control (A), PA pneumonia (B), immunosuppression (C) and immunosuppression with PA pneumonia (D). Mice were sacrificed at 4, 8 and 24 h after establishing experimental models. The pathological changes of lung tissue were graded, and the FOXP3 mRNA and serum IL-10 levels were detected. Histological analysis of lung tissues showed there were no significantly pathological changes in groups A and C, but significantly pathological changes were found in groups B and D, especially in group D at 8 h (P<0.05). The expression levels of FOXP3 mRNA in groups A and C showed no significant changes at the three time points, which were significantly lower than those in groups B and D (P<0.05). FOXP3 mRNA levels were lowest at 4 h, and there was significant difference between groups B and D (P<0.05). The serum levels of IL-10 in groups A and C were almost normal at the three time points, but decreased significantly in groups B and D (P<0.05). The serum levels of IL-10 decreased to the lowest at 8 h, especially in group D (P<0.05). The results indicate that PA pneumonia in immunosuppressive individuals worsens rapidly, which may be associated with Treg cells function disturbance. And Treg cells may be promising as adjuvant therapeutics for PA pneumonia in immunosuppressive individuals.
Keywords: immunosuppression; pneumonia; pseudomonas aeruginosa; regulatory T cells.