Reduced levels of interleukin‑1 receptor antagonist act as a marker for pneumonia in the elderly.

Pneumonia is a disease causing serious inflammation and infection of the lungs and accounts for >50,000 mortalities annually. The elderly are at an increased risk of developing pneumonia. Pneumonia is more serious in the elderly than in any other age group due to the increased inflammation and risk of community‑acquired pneumonia associated with aging. Interleukin‑1 receptor antagonist (IL‑1RA) is an anti‑inflammatory protein that counteracts the destructive effects of inflammatory proteins. Therefore, the possible association between pneumonia in elderly individuals and reduced levels of IL‑1RA was investigated in the present study. The number of lymphocytes was counted in all subjects and the relative protein expression levels of IL‑1RA were determined using western blot analysis. In addition, the immunological activities of IL‑1RA were measured using ELISA. The results demonstrated that the numbers of lymphocytes in the serum and bronchoalveolar lavage fluid (BALF) were significantly higher in elderly patients than those in young patients. Furthermore, the serum and BALF levels of IL‑1RA in elderly patients were significantly lower than those in young patients (P<0.05 and P<0.01, respectively). Therefore, reduced levels of IL‑1RA in BALF may act as a marker for pneumonia in the elderly and may be a potential adjuvant for the diagnosis of pneumonia in elderly individuals. The results also showed that smoking was associated with significant reductions in the levels of IL‑1RA in the BALF of elderly patients. The association between smokers and non‑smokers found in this study provides support for the hypothesis that smoking may contribute to the pathogenesis of pneumonia by further reducing IL‑IRA levels in certain elderly patients.