Expressão de células T regulatórias, citocinas e alteração hormonal do colostro de mães com giardíase

Abstract

The protozoan parasite Giardia lamblia infects humans and other mammals by ingesting water and/or food contaminated with cysts. Giardiasis affects people all over the world, especially children, and is one of the main causes of diarrhea in the world. Through colostrum and breast milk, newborns receive several bioactive components that can boost their immune system and prevent diarrheal diseases. Among these components are immunoregulatory elements, such as regulatory T cells (Tregs), cytokines IL-10 and TGF-β, and hormones, including cortisol and melatonin, with immunomodulatory capacity, which participate in various aspects related to the immune system and constitute an important defense mechanism for protection and treatment of parasitic diseases. There is a scarcity in the literature of studies on the regulatory mechanisms involved during giardiasis, especially associated with breastfeeding, as well as the effect of the hormones cortisol and melatonin on Tregs cells during interactions with Giardia lamblia. Thus, the aim of this study was to evaluate the immunoregulatory mechanisms involved in Giardia lamblia infection, as well as the concentration of the hormones melatonin and cortisol in colostrum from giardiasis-seropositive mothers. Colostrum samples were collected from nursing mothers between the ages of 18 and 35 years. The pregnant women were divided into two groups according to seropositivity for IgM and IgG anti-Giardia lamblia, determined by ELISA test, being the control group (IgG and IgM non reagent N=6) and (IgG reagent N=6 and IgM reagent N=5). By means of ELISA the concentrations of the hormones melatonin and cortisol present in the colostrum supernatant were evaluated. The concentrations of the cytokines IL-10 and TGF-β in the supernatant were determined by flow cytometry, as well as the immunophenotyping of regulatory T cells (CD4+CD25+FOXP3+) present in colostrum. In the group seropositive for IgM anti-G. lamblia the concentration of the hormone melatonin was lower when compared to the seronegative group, while in the colostrum of mothers seropositive for IgG anti-G. lamblia the concentration of melatonin was higher. The percentage of regulatory T cells was higher in colostrum from anti-G. lamblia IgM reagent mothers, as was the concentration of TGF-β in this same group. In colostrum from anti-G. lamblia IgG-seropositive mothers, the concentration of the hormone cortisol, percentage of regulatory T cells, and concentration of the cytokines IL-10 and TGF-β were similar to those found in colostrum from seronegative mothers. There was a positive correlation between melatonin concentration and percentage of Tregs cells in the seronegative group. These results suggest a possible action of melatonin in counterbalancing the immunoregulatory response in G. lamblia infection.