Background: Although radiological features of pneumocystis pneumonia (PCP) in non-Acquired Immune Deficiency Syndrome (AIDS) immunocompromised patients have been reported by other authors, there were no studies on the radiological stages of PCP previously. This study aimed to elucidate the radiological stages and prognoses of PCP in non-AIDS immunocompromised patients. Methods: Retrospective analysis of radiological manifestations and prognoses of 105 non-AIDS PCP immunocompromised patients from August 2009 to April 2016 was conducted. Chest radiograph was divided into three stages: early stage (normal or nearly normal chest radiograph), mid stage (bilateral pulmonary infiltrates), and late stage (bilateral pulmonary consolidations); chest high-resolution computed tomography (HRCT) was also divided into three stages: early stage (bilateral diffuse ground-glass opacity [GGO]), mid stage (bilateral diffuse GGO and patchy consolidations), and late stage (bilateral diffuse consolidations). Results: The case fatality rate (CFR) of all patients was 34.3% (36/105), all of them took routine chest X-ray (CXR), and 84 underwent chest CT examinations. According to the CXR most near the beginning of anti-PCP therapy, 18 cases were at early stage and CFR was 0 (0/18, P< 0.01), 50 cases were at mid stage and CFR was 28.0% (14/50, P> 0.05), and 37 cases were at late stage and CFR was 59.5% (22/37, P< 0.01). According to the chest HRCT most near the beginning of anti-PCP therapy, 40 cases were at early stage and CFR was 20.0% (8/40, P> 0.05), 34 cases were at mid stage and CFR was 47.1% (16/34, P> 0.05), and 10 cases were at late stage and CFR was 80.0% (8/10, P< 0.05); barotrauma, including pneumothorax, pneumomediastinum, and pneumohypoderma, was found in 18 cases and the CFR was 77.8% (14/18, P< 0.01). Conclusions: Based on the radiological manifestations, the course of PCP in non-AIDS immunocompromised patients can be divided into three stages: early stage, mid stage, and late stage. The prognoses of patients treated at early stage are good, and those at late stage are poor. Furthermore, the CFR of patients with barotrauma is high.

Pneumocystis pneumonia constitutes a critical life-threatening opportunistic infection, where the host's immune response plays a central role in its pathogenesis. Immunocompetent individuals are typically capable of eradicating Pneumocystis without exhibiting clinical symptoms. In contrast, individuals with compromised immune systems are vulnerable to developing Pneumocystis pneumonia, which can lead to severe inflammatory responses and consequent pulmonary damage. This review examines the roles of innate immunity, particularly macrophages and adaptive immunity, including CD4⁺ and CD8⁺ T-cells, as well as key cytokines, in the defence against Pneumocystis infection across various host categories, namely immunocompetent individuals, those infected with HIV and non-HIV-infected individuals, especially those undergoing corticosteroid therapy. By integrating findings from animal models and clinical studies, this review seeks to enhance our understanding of the pathogenesis of Pneumocystis infection across varied immunological contexts.

Background: Myeloid-derived suppressor cells (MDSCs) have been reported to expand and have a potent ability in the expansion of regulatory T cells in malignant and infectious disease. The current study was performed to investigate the role of MDSCs and possible immune mechanisms in dampening immune responses of community acquired pneumonia (CAP). Methods: This was a single-center cross-sectional study. The distribution of MDSCs subsets, the PD-1/PD-L1(L2) level of MDSCs subsets and Tregs in the peripheral blood of adult CAP patients and healthy control were measured by flow cytometry analysis. Results: Peripheral blood mononuclear cells (PBMCs) from 63 adult CAP patients contained an elevated frequency of both G-MDSC (4.92±0.30 vs 2.25±0.21,p<0.0001) and M-MDSC (19.40±1.30 vs 9.64±0.57,p<0.001) compared to healthy controls. Treg in the peripheral blood of CAP patients exhibited increased expression of PD-1 and CTLA-4, accompanied by no difference of their frequency. Moreover, up-regulated expression of PD-L1 on MDSC subsets in the peripheral blood of CAP patients was also revealed. Of note, the frequency of circulating MDSCs subset displayed a positive correlation with neutrophil count percentage in blood in CAP patients. Conclusions: In summary, the significant expansion of circulating MDSCs subsets and the up-regulated expression of PD-1/PD-L1 level in CAP patients may suggest the possible involvement of PD-1/PD-L1axis in MDSCs mediated immune regulation on Treg at least partially in CAP patients.