Comparative Phenotypic and Functional Analyses of the Effects of IL-10 or TGF-β on Porcine Macrophages

Macrophages are phagocytic cells involved in maintaining tissue homeostasis and defense
against pathogens. Macrophages may be polarized into different functionally specialized subsets.
M2c macrophages arise following stimulation with IL-10 or TGF- and mediate anti-inflammatory
and tissue repair functions. M2c macrophages remain poorly characterized in the pig, thus we
investigated the impact of these regulatory cytokines on porcine monocyte-derived macrophages
(moMF). The phenotype and functionality of these cells was characterized though confocal microscopy,
flow cytometry, ELISA, and RT-qPCR. Both cytokines induced CD14 and MHC II DR
down-regulation and reduced IL-6, TNF-, and CD14 expression, suggestive of an anti-inflammatory
phenotype. Interestingly, neither IL-10 or TGF- were able to trigger IL-10 induction or release by
moMF. Differences between these cytokines were observed: stimulation with IL-10, but not TGF-,
induced up-regulation of both CD16 and CD163 on moMF. In addition, IL-10 down-regulated
expression of IL-1 and IL-12p40 4h post-stimulation and induced a stronger impairment of moMF
ability to respond to either TLR2 or TLR4 agonists. Overall, our results provide an overview of
porcine macrophage polarization by two immunosuppressive cytokines, revealing differences between
IL-10 and TGF-, and reporting some peculiarity of swine, which should be considered in
translational studies.