Mendelian randomization analysis of two samples to determine the impact of immune cells on bronchitis

Bronchitis is a common respiratory disease characterized by acute inflammation, edema, and necrosis of the small airways, leading to a significant pathological burden. Immune cells play a crucial role in combating bronchitis. This study aims to explore the causal relationship between immune cells and bronchitis using the Mendelian randomization approach. In this study, we screened 18,183 single nucleotide polymorphisms highly associated with immune cells and employed 5 Mendelian randomization methods to assess the potential causal link between different types of immune cells and bronchitis. Additionally, the study utilized inverse variance weighting and MR-Egger regression analysis to evaluate the heterogeneity and robustness of the causal estimates. The study found a significant causal association between 28 types of immune cells and the risk of bronchitis. These cell types mainly included T cells, monocytes, and B cells. For instance, CD25 on B cells and CD25 on IgD+ were associated with an increased risk of bronchitis, whereas IgD+ CD24- B cells and CD33- HLA DR- AC showed a protective effect against bronchitis. Moreover, the study validated the robustness of these findings through leave-one-out analysis and the MR-Egger method, and quantitatively illustrated the impact of immune cells on the risk of bronchitis through forest plots. This study reveals the dual role of immune cells in bronchitis. The identified types of immune cells may increase the risk of bronchitis by promoting inflammatory responses and cell-mediated immune reactions, while other cell types may offer protection by promoting immune balance and effective defense.