Th17 lymphocytes and Interleukin-17A during the course of severe community acquired pneumonia, comparison with etiology and outcome.

Objective: Observational study of patients diagnosed with severe community acquired pneumonia (sCAP) carried out to evaluate levels of interleukin 17A (IL-17A) and T helper 17 (Th17) lymphocyte count in peripheral circulation and bronchoalveolar lavage fluid (BALF) in the early course of sCAP of different etiology and to compare them with patient's characteristics and outcome.

Material and methods: Cohort of 74 patients with sCAP was analyzed and respective microbial etiology established. According to pathogens, 3 subgroups of patients were created: bacterial, viral and mixed etiology. Th17 count and IL-17A levels were measured using flow cytometry and ELISA in peripheral blood and BALF. Data were compared with respect to etiology and their correlation with 30and 90-day mortality was statistically analyzed.

Results: There was no statistically significant correlation in Th17 count and IL-17A levels in blood and BALF between etiological subgroups of CAP and no correlation was found with respect to measured parameters and 30and 90-day mortality. Nevertheless, increased Th17 cell count and IL-17A levels in peripheral blood, but not in BALF, in the early course of sCAP are correlated with increased relative risk of death from sCAP. Other factors increasing relative risk of death in patients with sCAP found in our cohort were male sex and advanced age.

Conclusions: Systemic Th17 count and IL-17A levels in the early course (up to 7 days from admission) of sCAP may be correlated with severity and outcome of sCAP.