Interrelationships of interleukin-8 with interleukin-1β and neutrophils in vaginal fluid of healthy and bacterial vaginosis positive women

Vaginal innate immunity in response to microbial perturbation is still poorly understood and could be crucial for protection from adverse outcomes. We investigated the relationship between interleukin (IL)-8, IL-1β and neutrophils in vaginal fluid obtained from 60 healthy women and 51 women who were bacterial vaginosis (BV) positive. Concentrations of IL-8 and IL-1β were highly correlated with counts of neutrophils in vaginal fluid of the entire population examined (111 subjects). Vaginal IL-1β concentrations were significantly higher (P <0.001) in BV positive women. There was no significant difference in IL-8 levels or number of neutrophils between healthy controls and BV positive women. None of the healthy controls with high neutrophil counts (≥75th percentile, 14 average count per field) had high concentrations of IL-1β (≥75th percentile, 220 pg/ml), whereas 84% of BV positive women with high neutrophil counts had high IL-1β concentrations (P <0.001). On the contrary, no difference in the percentage of subjects with elevated concentrations of IL-8 (≥75th percentile, 2842 pg/ml) was found between healthy and BV positive women with high numbers of neutrophils (55.5% of healthy versus 53% of BV positive women). Our findings show that BV causes a large increase in IL-1β concentrations which is not paralleled by an increase in IL-8 concentrations in vaginal fluid, suggesting that BV-associated factors more specifically dampen IL-8 rather than IL-1β. The lack of an increase in IL-8 may explain the absence of an increase in neutrophil numbers in most women exposed to abnormal vaginal colonization (BV).