Interleukin-1 receptor antagonist gene polymorphism, vaginal interleukin-1 receptor antagonist concentrations, and vaginal Ureaplasma urealyticum colonization in pregnant women

Ureaplasma urealyticum is the microorganism most frequently isolated from amniotic fluids of women in preterm labor. The relationship between vaginal colonization with U. urealyticum, vaginal interleukin-1 receptor antagonist (IL-1ra) levels, and the IL-1ra genotype in pregnant women was examined. Vaginal specimens, obtained with a cotton swab from 207 women in their first trimester of pregnancy, were tested for IL-1ra concentrations by enzyme-linked immunosorbent assay and for U. urealyticum and IL-1ra genotypes by PCR. U. urealyticum was detected in 85 (41.1%) women. The median IL-1ra level was 450 ng/ml in women positive for U. urealyticum, as opposed to 225 ng/ml in women negative for this microorganism (P < 0.0001). Sixty-two percent of the 16 women who were homozygous for allele 2 of the IL-1ra gene (IL-1RN*2) were colonized with U. urealyticum, as opposed to 47% of the 49 women who were IL-1RN*1/IL-1RN*2 heterozygotes and 34% of the 133 women who were IL-1RN*1 homozygotes (P < 0.05). Median IL-1ra levels were 750 ng/ml in IL-1RN*2 homozygotes, 300 ng/ml in IL-1RN*1/IL-1RN*2 heterozygotes, and 50 ng/ml in IL-1RN*1 homozygotes (P = 0.02). The vast majority of subjects had an uneventful pregnancy and delivered a healthy infant at term. The IL-1ra genotype or U. urealyticum colonization was unrelated to birth weight. Pregnant women who are colonized with U. urealyticum during the first trimester have elevated vaginal IL-1ra concentrations and a higher prevalence of the IL-1RN*2 homozygote genotype than do noncolonized women.