Cytokine induced expression of programmed death ligands in human neutrophils.

Recent evidence indicates that human neutrophils can serve as non-professional antigen presenting cells (APC). Although expression of MHC class II and co-stimulatory molecules on human neutrophils is limited, these molecules can be significantly induced following in vitro exposure to the cytokines IFNgamma and GM-CSF. Since professional APCs such as dendritic cells express both co-stimulatory and co-inhibitory molecules for activation and regulation of adaptive immunity, we determined whether cytokines induce increased expression of specific co-signaling molecules on human neutrophils. We report here that circulating human neutrophils express co-inhibitory molecules such as immunoglobulin-like transcript (ILT) 4 and 5, and also comparatively low and highly variable levels of ILT2 and ILT3, but the expression of these ILTs was not significantly changed by cytokine treatment. In contrast, we demonstrate for the first time that human peripheral blood neutrophils, although do not express the co-inhibitory molecule, programmed death ligand (PD-L) 1 on their surface, can express this molecule at moderate levels following cytokine exposure. Although moderate PD-L1 levels on healthy volunteers' neutrophils were not inhibitory to T cells, our findings do not exclude a possible robust increase in neutrophil PD-L1 expression in pathological conditions with immunosuppressive functions. These results suggest a possible immunoregulatory role for human neutrophils in adaptive immunity.

The incidence and clinical significance of pneumomediastinum found on computed tomography scan in blunt trauma patients.

With the increased use of chest computed tomography (CT) scan in the initial evaluation of major trauma, findings that were not seen on a chest radiograph (CXR) are increasingly identified. Pneumomediastinum (PM) seen on CXR in blunt trauma patients is considered worrisome for airway and/or esophageal injury. The purpose of this study was to determine the incidence and clinical significance of PM found on CT in blunt trauma patients. Blunt trauma patients admitted to a single Regional Trauma Center over a 2-year period were identified. Records were reviewed for demographics, mechanism, diagnostic evaluations, injuries, and outcome. A total of 2052 patients met study criteria. Fifty-five (2.7%) had PM; 49 patients (89%) had PM identified on CT alone, whereas six patients (11%) had it identified on both CXR and CT. There was no significant difference in gender or age between the two groups. Associated injuries were similar between groups. No patients had tracheobronchial or esophageal injuries. In this study, PM seen on CT was found to have little clinical significance other than as a marker for severe blunt trauma. No patients with airway or esophageal injuries were seen in any of the PM patients.