Assessment of local humoral immunity status in oral fluid of smokers: a cross-sectional study

BACKGROUND: The oral cavity is constantly exposed to antigens. Local humoral immunity, mediated primarily by secretory immunoglobulin A (sIgA), plays a pivotal role by binding these antigens. The relationship between sIgA levels and the intensity of chronic inflammation is actively studied. Given that smoking is a factor of chronic oral inflammation, it is important to evaluate the local humoral immunity (sIgA) status and its association with inflammation activity (IL-6) in the oral fluid of smokers. AIM: To assess the local humoral immunity and chronic inflammation activity using sIgA and IL-6 levels in the oral fluid of smokers. METHODS: A smoking history survey was conducted among third-year students of the Dentistry Department at the Pavlov First Saint Petersburg State Medical University. The study also included a detailed history of the local oral mucosa status (acute infections, chronic diseases of the oral mucosa and throat) and immunity disorder and allergy history. The levels of sIgA and IL-6 in oral fluid were determined by enzyme immunoassay. RESULTS: A total of 29 respondents were included in the study: 11 smokers and 17 non-smokers (control group). One respondent was excluded from the study due to acute respiratory viral infection. The average smoking history was 3 years; 54.5% of smokers (n = 6) and 66.7% of non-smokers (n = 12) had an allergy history. No immunodeficiencies were observed. Chronic gingivitis (K05.1) was diagnosed in one smoker. Chronic tonsillitis (J35.0) was diagnosed in two smokers. Oral fluid sIgA levels were lower in smokers than in non-smokers (31.25 [15.43; 96.20] vs 89.04 [64.73; 120.36] ng/mL, p = 0.04 [negligible]). There was no significant difference in the IL-6 level (12.74 [8.63; 17.56] vs 9.69 [7.90; 20.61], p = 0.36). For statistical analysis, the median and quartiles were used, as the groups were small and the distribution was different from normal (as assessed by the Shapiro–Wilk test). For comparative analysis, we used the Mann–Whitney U test. Enzyme immunoassay was performed using Vector-Best kits (Russia). CONCLUSION: The findings indicate that smokers have lower levels of sIgA in oral fluid than non-smokers, which may contribute to chronic inflammatory diseases of the oral mucosa and throat in smokers.