Differences in immune function and cytokine levels among children in different age groups with severe community-acquired pneumonia.

The aim of this study is to examine the variations in immune function and cytokine profiles among children with severe community-acquired pneumonia (SCAP) across different age groups, and to investigate the immunological factors contributing to the increased risk of severe illness and mortality in younger children. The study found that age-related trends in CD3 + T lymphocytes (%), CD4 + T lymphocytes (%), CD8 + T lymphocytes (%), CD4+/CD8 + T cell ratio, B cells (%), immunoglobulin G (IgG), immunoglobulin A (IgA), and complement 3 (C3) in children with SCAP were similar to those observed in healthy children. However, the trends for natural killer(NK) cells (%) and complement 4(C4) in children with SCAP differed from those in healthy children. Additionally, immunoglobulin M (IgM) levels in children with SCAP showed no correlation with age, and no consistent age-related trend was observed in healthy children. Moreover, Interleukin-8 (IL-8) and Interleukin-10 (IL-10) levels were negatively correlated with age in children with SCAP, while age-related trends for these cytokines in healthy children have not been documented. Overall, most of our findings align with existing data on healthy children. This study reveals that the age-related changes in immune function observed in healthy children closely resemble those seen in children with SCAP. This suggests that the age-dependent nature of immune function in children not only correlates with a higher incidence rate among younger populations but may also indicate that an earlier age of onset is associated with a greater likelihood of disease exacerbation. Furthermore, it was noted that the younger the age of onset, the higher the levels of IL-10 and IL-8 in peripheral blood.