Expressão do complexo de histocompatibilidade principal de classe I não clássico na placenta bovina ao longo da gestação e após infecção por Brucella abortus

Abstract

Nonclassical Major Histocompatibility Complex Class I genes are monomorphic or oligomorphic and have restricted cellular expression. Moreover, their products seem to have different functions, among them, act as ligands for inhibitory receptors of the natural killer complex during pregnancy, protecting the fetus from maternal rejection. Considering the hypothesis that occurs variable nonclassical MHC-I expression in different regions of the bovine placenta throughout pregnancy and that the interaction between Brucella abortus and trophoblast cells alters the expression profile of these genes, this study aimed to characterize the expression of nonclassical MHC-I in bovine placenta throughout pregnancy, as well as verify these expression in trophoblast cells during the third trimester of pregnancy after infection with B. abortus. The RNA extracted from placentome and intercotiledonary region of cows during the first (n=6), second (n=6) and third (n=6) trimesters of pregnancy, was subjected to RT-PCR. Explants were prepared from chorioallantoic membrane, and two experimental groups were determined: control and infected. Infection was performed with the reference sample B. abortus 2308 (1.0 x 107 CFU) for four hours to assess the gene profile expression. The non-classical MHC-I genes MICB and NC3 had higher levels of transcription in the intercotyledonary region when compared to the placentome, which higher levels of transcription at the second trimester of gestation. NC1 and classical MHC-I had very low levels of transcription. Trophoblastic cells of B. abortus-infected chorioallantoic membrane explants had a mild increase in transcription of non-classical MHC-I at 4 h post infection. Therefore, this study provides a thorough analysis of nonclassical MHC-I transcription at different stages of gestation and different placental tissues, with an increased transcription of some non-classical MHC-I genes, mostly in the intercotyledonary region at mid gestation. Furthermore, this study demonstrated that B. abortus infection is associated with mild upregulation of non-classical MHC-I in bovine placental tissues.