Mycobacterium vaccae immunization to OVA sensitized pregnant BALB/c mice suppressed placental and postnatal IL-5 and inducing IFN-gamma secretion

Although the development of atopy in the newborn is determined by a multitude of factors, an intense Th1 stimulus early in life could be protective by facilitating a switch away from Th2. Aimed to determine the effect of single Mycobacterium vaccae (M. vaccae) immunization to OVA-sensitized pregnant mice on IL-5 and IFN-γ secretion from placental lymphocytes and splenocytes of offspring.

Pregnant BALB/c mice were divided into 4 groups, OVA-sensitized + M. vaccae immunized, OVA-sensitized, M. vaccae immunized and controls. Sensitization with OVA was initiated before mating, and aerosol OVA challenge were performed during pregnancy. M. vaccae immunization was performed on the 12^th day of pregnancy. IL-5 and IFN-γ levels of placental lymphocytes were analyzed on the 18^th day of pregnancy and splenocytes of offspring on the 2^nd and 28^th days during postnatal period. A single administration of M. vaccae to OVA-sensitized pregnant mice downregulated IL-5 secretion and induced IFN-γ secretion from placental lymphocytes. On the other hand, after M. vaccae immunization downregulation of IL-5 levels and upregulation of IFN-γ secretion persisted in offspring when determined on 2^nd and 28^th days of life. Vaccination with M. Vaccae to OVA-sensitized pregnant BALB/c mice prevented Th2 immune responses by enhancing secretion of IFN-γ and lowering IL-5 levels during pregnancy and the effect persisted during the postnatal period in offspring.