Abstract
While smoking-induced epigenetic changes are increasingly recognized, the relationship between varying smoking history and immune protein profiles remains incompletely understood. This study investigates associations between smoking history and circulating inflammatory cytokines and serum immunoglobulins, and explores DNA methylation as a potential mediator. We analyzed 2,119 participants from the Rotterdam Study, examining associations of smoking duration, pack-years, and cessation time with plasma inflammatory proteins, including six pro- and three anti-inflammatory cytokines (Olink) and three serum immunoglobulins (IgA, IgG, and IgM). Cytokines were z-transformed and multivariable (non)linear regression models were applied, adjusted for age, sex, BMI, alcohol use, and socioeconomic status. A distinct immune signature emerged, with (z-transformed) IL-6, IL-18, IL-17C, and IL-10 levels increasing with pack-years and smoking duration (β range: 0.0029 to 0.015). IgA and IgG displayed reverse J-shaped associations with pack-years (β range: –0.050 to 0.048) and levels declined with smoking duration (β = –0.0067 and –0.028, respectively). IL-6, IL-17A, and IL-10 decreased with cessation time (β range: -0.007 to -0.004), and IgG increased (β = 0.018). IgM responses differed by sex. Mediation analysis using PCA-derived CpG components did not support a role for DNA methylation in these associations. These findings reveal dose-dependent, pro-inflammatory immune dysregulation with cumulative smoking exposure and partial reversibility of IL-6 and IgG following cessation. The absence of mediation by DNA methylation suggests other pathways are involved. These findings support the use of cytokines and immunoglobulins as biomarkers for immune surveillance and recovery monitoring, reflecting an underlying inflammatory smoking signature. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10875-025-01975-y.