Transforming Growth Factor-? Activation and Signaling in the Alveolar Environment during Pneumocystis Pneumonia

The importance of pro-inflammatory and anti-inflammatory cytokines in Pneumocystis jirovecii pneumonia

The role of pro-inflammatory and anti-inflammatory cytokines in Pneumocystis jirovecii pneumonia (PcP) of non-AIDS immunocompromised patients remains unclear. We measured the levels of pro-inflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, monocyte chemoattractant protein-1 (MCP-1) and anti-inflammatory cytokines including IL-10 and transforming growth factor (TGF)-β1 in bronchoalveolar lavage fluid (BALF) and blood in 36 non-AIDS immunocompromised patients with PcP diagnosed by BAL and explored their clinical importance. The severity of PcP was determined by arterial oxygen tension/fraction of inspired oxygen concentration (PaO2/FiO2) ratio, the need of mechanical ventilation and the death. Twenty-five subjects without evidence of lung abnormality were included as control group. Compared with control group, PcP patients had significantly higher BALF levels of IL-1β, TNF-α, IL-6, IL-8 and MCP-1 and significantly higher blood levels of IL-10, TGF-β1, IL-8, IL-6 and MCP-1. For PcP patients, BALF levels of IL-8, IL-8/IL-10 ratio and IL-8/TGF-β1 ratio and blood levels of IL-8 and IL-8/IL-10 ratio were significantly higher in the patients with PaO2/FiO2 < 200 mmHg than in those with PaO2/FiO2 > 200 mmHg. Similarly, significantly higher BALF levels of IL-8, IL-8/IL-10 ratio, IL-1β/IL-10, IL-1β/TGF-β1 ratio, MCP-1/TGF-β1 ratio and IL-8/TGF-β1 ratio were found in the patients requiring mechanical ventilation and in non-survivors. In summary, an imbalance of pro-inflammatory and anti-inflammatory cytokines in BALF was found in PcP of non-AIDS immunocompromised patients. BALF levels of IL-8, IL-8/IL-10 ratio, IL-1β/IL-10 ratio, IL-1β/TGF-β1 ratio, MCP-1/TGF-β1 ratio and IL-8/TGF-β1 ratio may be of value in assessing the severity of PcP and in predicting the outcome of the patients.

Interleukin-1 promotes coagulation, which is necessary for protective immunity in the lung against Streptococcus pneumoniae infection

Interleukin (IL)-1 is a well-known cytokine for the initiation of innate immunity in bacterial infection. However, the underlying mechanism of IL-1 on the respiratory infection is not fully elucidated. We studied how IL-1 contributes to the host defense against Streptococcus pneumoniae. IL-1R(-/-) mice showed high mortality, local cytokine storm, and substantial infiltrates in the lower respiratory tract after intratracheal challenge with S. pneumoniae. The IL-1-deficient condition did not suppress the propagation of bacteria in the lung, although the recruitment and the bacteria-killing ability of neutrophils (CD11b(+)Ly6C(+)Ly6G(+)) were not defective compared with wild-type mice. Unexpectedly, we found that the transcription of fibrinogen alpha and gamma genes were highly activated in the lungs of wild-type mice after the infection, whereas no significant changes were found in IL-1R(-/-) mice. Of note, synthesis of fibrinogen was dependent on the IL-1-IL-6-Stat3 cascade. Treatment with recombinant fibrinogen improved survival and bacterial propagation in the IL-1R(-/-) mice and blockade of the coagulation increased the susceptibility of wild-type mice to pneumococcal pneumonia. Our findings suggest that IL-1 signaling leads to the synthesis of fibrinogen in the lung after pneumococcus infection and is followed by coagulation, which contributes to the control of bacterial infection in the pulmonary tract.

Cellular and cytokine changes in the alveolar environment among immunocompromised patients during Pneumocystis jirovecii infection

Limited data exist on the cytokine and cellular changes in the alveolar environment in immunocompromised patients during Pneumocystis jirovecii infection. A cellular and a cytokine analysis were performed on bronchoalveolar lavage (BAL) samples from three groups of patients, i.e., an initial study group of 64 immunocompromised P. jirovecii-positive individuals and two control groups of P. jirovecii-negative patients who had been or not immunosuppressed (65 patients). The results were related to alveolar dilution as determined by urea measurement. Compared with non-infected groups, P. jirovecii-infected patients had a lower level of alveolar macrophages (AM), particularly those with high burdens of P. jirovecii. Alveolar macrophages over-expressed the Dectin-1 receptor, which was largely implicated in P. jirovecii clearance. The alveolar CD8+T and CD4+T lymphocyte counts were increased and an inverse correlation was observed between the alveolar CD4+ cell count and the P. jirovecii burden. Although the alveolar IL-6 level was considerably increased, alveolar IL-17, IL-10, TNF-α, TGF-β concentrations of P. jirovecii patients were not different from the control groups. Changes in the pulmonary environment were also highlighted during P. jirovecii colonization. Our study suggests that there is a correlation between the P. jirovecii burden in the alveolus (from colonization to a high P. jirovecii burden), and the degree of impairment of the alveolar immune response.