Distinct phenotypic features of neonatal murine macrophages

Abstract

Neonates rely on their innate immune system. Resident tissue macrophages are considered to be initiators and regulators of the innate immune response and thus, appear to be especially important to neonates. We hypothesized that the phenotype and function of neonatal tissue macrophages differ from their adult counterparts. Peritoneal macrophages from neonatal (<24 h) and adult (6 weeks old) C57BL/6J mice were isolated and analyzed by high-content chipcytometry. After stimulation for 6 h with LPS (0, 1, 10, 100 ng/mL), macrophage transcriptome was analyzed by microarray and cytokine release was measured using multiparametric bead assays. Antigen presenting capacity was compared by T-cell stimulation assays. We observed that neonatal murine peritoneal macrophages are characterized by selective lack of expression of F4/80, MHC class II, and costimulatory molecules (CD80, CD86). Furthermore, we found differences in the transcriptome between neonatal and adult macrophages, unstimulated and after LPS stimulation. Although neonatal macrophages showed a significantly increased secretion of proinflammatory cytokines upon LPS stimulation, their potential to induce T-cell proliferation was significantly reduced. In conclusion, we observed a distinct phenotype of the neonatal macrophage population. The specific functions of this macrophage population could help to understand the excessive inflammatory reactions observed in the very young.Keywords: Immune responses r Macrophages r Neonate immunity r Toll-like receptors (TLRs) Additional supporting information may be found in the online version of this article at the publisher's web-site IntroductionNeonates and in particular preterm infants are extremely vulnerable to states of inflammation [1]. They have an increased susceptibility to microbial infections with an enhanced morbidity and Correspondence: Mr. Thomas Winterberg e-mail: Winterberg.thomas@mh-hannover.de mortality [2]. Sepsis, pneumonia, and gastrointestinal disorders such as necrotizing enterocolitis are a common threat to patients in neonatal intensive care. The first days of life represent a period of transition of the immune system: The protection of the fetus by the maternal immune system and the sterile environment are lost and the newborn has to cope with the outside world and its multiple foreign antigens. Although maternal antibodies help the neonate in the first weeks, it has to develop its own adaptive immune capacities during infancy [2]. In the neonatal period, monocytes and [6][7][8][9]. Until now, neonatal monocytes and macrophages have been described as immature or dormant myeloid cells. However, these studies are based on peripheral blood monocytes or CBMs, which further differentiate into macrophages ex vivo. Little is known about tissue macrophages in neonates, due to technical difficulties of their isolation and evaluation, but a recent study demonstrated their unique function during heart tissue regeneration [10].It has been shown that the heterogeneous murine macrophage populations are orig...

Conventional alpha beta (αβ) T cells do not contribute to acute intestinal ischemia-reperfusion injury in mice

“…Gut cryosections (2 μm) were prepared for immunohistochemistry and processed as previously described with the following primary antibodies rat anti-mouse GR-1, rat anti-mouse F4/80 and anti-CD3 (Clone: 145-2C11) (AbD Serotec, Oxford, UK) [23]. Cytospin preparations of 10 5 cells were prepared (10 min,600 g) and stained according to May-Gruenwald-Giemsa and analyzed with an Olympus CKX41 light microscope (Shinjuku, Tokyo, Japan) [24]. …”

The phenotype and function of preterm infant monocytes: implications for susceptibility to infection

“…These studies have assessed the expression of these molecules at the protein level by flow cytometry and differences in staining protocols or gating strategies may contribute to the inconsistency of the findings. Collectively, reduced expression of antigen presentation and costimulatory molecules may lead to an increased susceptibility to infection through a reduced capacity to induce T cell proliferation [78].…”

The innate immune response to lower respiratory tract E. Coli infection and the role of the CCL2-CCR2 axis in neonatal mice

“…Childhood death and morbidity from microbe-induced pneumonia occurs most frequently during the first year of life, a period of rapid postnatal lung growth [2]. One possible reason for neonates and infants having greater morbidity and mortality from lower respiratory tract infections (LRTI) is the relative immaturity of their innate and adaptive immune system [3,4]. A lack of conditioning of their immune response due to a paucity of environmental exposures and/or infectious challenges could affect the timing and intensity of responses that could contribute to the poorer outcomes.…”

“…These mice also had impaired induction of MHC class II expression on airway macrophages [7]. In addition, peritoneal macrophages from neonates and cord blood monocytes have also been shown to have lower expression of MHC class II molecules when compared to adult macrophages and monocytes [3,6,8]. A less robust innate immune response to pathogen associated molecular patterns (PAMPS) may also alter the neonate’s ability to mount an adequate immune response to infection [9].…”