Cytokine production by bovine adipose tissue stromal vascular fraction cells upon Neospora caninum stimulation.

In bovines few studies addressed the contribution of adipose tissue to the host immune response to infection. Here we evaluated the in vitro response of bovine adipose tissue stromal vascular fraction (SVF) cells to the protozoan parasite Neospora caninum, using live and freeze-killed tachyzoites. Live N. caninum induced the production of IL-6, IL-1ß and IL-10 by SVF cells isolated from subcutaneous adipose tissue (SAT), while in mesenteric adipose tissue (MAT) SVF cell cultures only IL-1ß and IL-10 production was increased, showing slight distinct responses between adipose tissue depots. Whereas a clear IL-8 increase was detected in peripheral blood leucocytes (PBL) culture supernatants in response to live N. caninum, no such increase was observed in SAT or MAT SVF cell cultures. Nevertheless, in response to LPS, increased IL-8 levels were detected in all cell cultures. IL-10 levels were always increased in response to stimulation (live, freeze-killed N. caninum and LPS). Overall, our results show that bovine adipose tissue SVF cells produce cytokines in response to N. caninum and can therefore be putative contributors to the host immune response against this parasite.

Modulation of Leptin and Leptin Receptor Expression in Mice Acutely Infected with Neospora caninum.

Neospora caninum is an apicomplexan parasite that in cattle assumes particular importance, as it is responsible for abortions reported worldwide. Leptin is an adipokine mainly secreted by adipocytes, which beside its role in maintaining metabolic homeostasis also has important effects in both innate and adaptive immunity. In previous work, we showed that mice chronically infected with N. caninum had elevated serum leptin levels. Here, we sought to assess whether acute infection with N. caninum infection influenced the production of this adipokine as well as leptin receptor mRNA levels. Our results show that acute infection with N. caninum led to decreased leptin serum levels and mRNA expression in adipose tissue. A decrease in leptin receptor transcript variant 1 mRNA (long isoform) and leptin receptor transcript variant 3 mRNA (one of the short isoforms) expression was also observed. An increase in the number of cells staining positive for leptin in the liver of infected mice was observed, although this increase was less marked in Interleukin (IL)-12/IL-23 p40-deficient mice. Overall, our results show that N. caninum infection also influences leptin production during acute infection.

Characterization of Myeloid Cellular Populations in Mesenteric and Subcutaneous Adipose Tissue of Holstein-Friesian Cows.

Immune cells resident in adipose tissue have important functions in local and systemic metabolic homeostasis. Nevertheless, these immune cell populations remain poorly characterized in bovines. Recently, we described diverse lymphocyte subpopulations in adipose tissue of Holstein-Friesian cows. Here, we aimed at characterising myeloid cell populations present in bovine adipose tissue using multicolour flow cytometry, cell sorting and histochemistry/immunohistochemistry. Macrophages, CD14+CD11b+MHC-II+CD45+ cells, were identified in mesenteric and subcutaneous adipose tissue, though at higher proportions in the latter. Mast cells, identified as SSC-AhighCD11b-/+CD14-MHC-II-CH138A-CD45+ cells, were also observed in adipose tissue and found at higher proportions than macrophages in mesenteric adipose tissue. Neutrophils, presenting a CH138A+CD11b+ phenotype, were also detected in mesenteric and subcutaneous adipose tissue, however, at much lower frequencies than in the blood. Our gating strategy allowed identification of eosinophils in blood but not in adipose tissue although being detected by morphological analysis at low frequencies in some animals. A population not expressing CD45 and with the CH138A+ CD11b-MHC-II- phenotype, was found abundant and present at higher proportions in mesenteric than subcutaneous adipose tissue. The work reported here may be useful for further studies addressing the function of the described cells.

T cells in mesenteric and subcutaneous adipose tissue of Holstein-Friesian cows.

The importance of immune cells present in the adipose tissue to metabolic homeostasis has been increasingly recognized. Nevertheless, in bovines few studies have so far addressed the immune cell populations resident in this tissue. Here we developed an eight-colour flow cytometry panel to address T cell populations present in bovine adipose tissue. Our results showed that γδ T cells, CD4+ and CD8+ CD3+ non-γδ T cells, as well as NK cells, are present in the mesenteric and subcutaneous adipose tissue of Holstein-Friesian cows. The frequency of both γδ T cells and CD8+ non-γδ T cells was found higher in mesenteric than in subcutaneous adipose tissue. The majority of T cells in adipose tissue presented a CD45RO+CD62L- phenotype, characteristic of effector memory cells, and the frequency of these cellular populations was higher than in the blood. The ratio of CD4+ T cells over CD8+ T cells was similar between subcutaneous and mesenteric adipose tissue but different from the one found in blood. Overall, our results highlight particular phenotypic characteristics of bovine adipose tissue T cell populations.