T-helper type 2 polarization among asthmatics during and following pregnancy

Asthma is the most common medical condition during pregnancy. While increased production of T helper cytokines has been reported to occur in both asthma and pregnancy, the effect of T-helper type 2 (Th2) polarization on asthma symptoms during pregnancy has not been well-characterized.

We hypothesized that systemic Th2 cytokine and chemokine polarization occurs among asthmatics to a greater extent during their pregnancy, and is associated with more severe asthma and increased Th2 polarization in the newborn.

Fifty-six pregnant asthmatics were recruited from prenatal clinics affiliated with New York Presbyterian Hospital. Systemic production of interleukin-4, interferon-gamma, eotaxin and IP10 were measured by intracytoplasmic staining or ELISA at recruitment, peripartum and post-partum, and in the cord blood. The frequency of asthma symptoms was measured by questionnaires and compared with Th biomarkers.

The chemokine ratio (IP10/eotaxin) declined over the course of pregnancy (from 3.3 +/- 1.3 to 1.4 +/- 0.2, P = 0.016), but IP10 and eotaxin increased post-partum. The decrease in the chemokine ratio was associated with more frequent asthma symptoms. A non-significant trend towards decreased interferon-gamma and increased interleukin-4 production was detected. Cord blood eotaxin levels correlated with maternal levels (r = 0.35, P = 0.03). Other peripartum biomarkers were not associated with Th2 polarization nor with subsequent respiratory symptoms in the newborn.

IP10/eotaxin declined over the course of pregnancy and was associated with worse asthma symptoms. Alterations of Th1/Th2 chemokine balance during pregnancy may identify women prone to more severe asthma during pregnancy.