Characterization of human peritoneal monocyte/macrophage subsets in homeostasis: Phenotype, GATA6, phagocytic/oxidative activities and cytokines expression

Abstract

Peritoneal macrophages play a critical role in the control of infectious and inflammatory diseases. Although recent progress on murine peritoneal macrophages has revealed multiple aspects on their origin and mechanisms involved in their maintenance in this compartment, little is known on the characteristics of human peritoneal macrophages in homeostasis. Here, we have studied by flow cytometry several features of human peritoneal macrophages obtained from the peritoneal cavity of healthy women. Three peritoneal monocyte/macrophage subsets were established on the basis of CD14/CD16 expression (CD14++CD16−, CD14++CD16+ and CD14highCD16high), and analysis of CD11b, CD11c, CD40, CD62L, CD64, CD80, CD86, CD116, CD119, CD206, HLA-DR and Slan was carried out in each subpopulation. Intracellular expression of GATA6 and cytokines (pro-inflammatory IL-6 and TNF-α, anti-inflammatory IL-10) as well as their phagocytic/oxidative activities were also analyzed, in an attempt to identify genuine resident peritoneal macrophages. Results showed that human peritoneal macrophages are heterogeneous regarding their phenotype, cell complexity and functional abilities. A direct relationship of CD14/CD16 expression, intracellular content of GATA6, and activation/maturation markers like CD206 and HLA-DR, support that the CD14highCD16high subset represents the mature phenotype of steady-state human resident peritoneal macrophages. Furthermore, increased expression of CD14/CD16 is also related to the phagocytic activity.

Phenotypic Switch of Human Peritoneal Macrophages during Childhood

“…For characterizing peritoneal macrophages in their homeostasis, it is crucial to develop methods for obtaining them in healthy humans. A new study that describes more detailed method for obtaining peritoneal macrophages from the peritoneal cavity of healthy women was recently published by Ruiz-Alcaraz et al 28,29 In a consecutive series of 212 women undergoing sterilization by tubal ligation or with benign gynecological pathologies, they obtained healthy peritoneal cell samples by laparoscopy or laparotomy. In that study, the primary umbilical trocar was established and then an accessory trocar was inserted in the right or left iliac fossa.…”

Isolation of functional mature peritoneal macrophages from healthy humans

“…Furthermore, two mouse peritoneal macrophages subpopulations, large (F4/80 high MHC-II low ) and small (F4/80 low MHC-II high ), with different phenotypes and functions have recently been described as residing in the mouse peritoneal cavity. With the method presented in this study, we are providing a tool that presents a reliable source to obtain mature tissue-resident macrophages in steady-state conditions 36 isolated from healthy individuals that could be used to compare the biology, phenotype and the role played by macrophages in different pathologies. 33,34 By contrast, small peritoneal macrophages, whose numbers increase noticeably under inflammatory conditions, appear to have originated from circulating monocytes.…”

“…32 Large peritoneal macrophages appear not to have originated from hematopoietic precursors and retain the capability to proliferate in situ to maintain physiological numbers, under steady-state conditions. 36 6,32,34 Similarly, in patients with decompensated cirrhosis the presence of three or two functionally and phenotypically distinct macrophage subpopulations has been described based on the expression of CD14 and CD16 29 or the C-C chemokine receptor type 2 and the complement receptor of the immunoglobulin superfamily, 35 respectively, that share similarities with large and small peritoneal macrophages from mice.…”

“…This has hampered our understanding of this key innate immune cell in human pathology. With the method presented in this study, we are providing a tool that presents a reliable source to obtain mature tissue-resident macrophages in steady-state conditions 36 isolated from healthy individuals that could be used to compare the biology, phenotype and the role played by macrophages in different pathologies. Thus, we have demonstrated that the peritoneal macrophages isolated following the described protocol displayed functional pathways such as phagocytic and oxidative activities and activated major proinflammatory pathways such as the NLRP3 inflammasome and the secretion of inflammatory cytokines.…”

“…This corroborates previous studies from our group which described how human peritoneal macrophages were able to induce the production of prostaglandins or sense hypotonic-induced volume changes to activate the NLRP3 inflammasome [37][38][39] and expressed both proinflammatory and anti-inflammatory (M1 and M2) polarization markers, suggesting a constitutive preactivated state that allows to quickly respond to any stimulus and to maintain homeostasis in the peritoneal cavity. 36…”