Induction of unique macrophage subset by simultaneous stimulation with LPS and IL-4

Abstract

Macrophages manifest as various subtypes that play diverse and important roles in immunosurveillance and the maintenance of immunological homeostasis in various tissues. Many in vitro studies divide macrophages into two broad groups: M1 macrophages induced by lipopolysaccharide (LPS), and M2 macrophages induced by interleukin 4 (IL-4). However, considering the complex and diverse microenvironment in vivo, the concept of M1 and M2 is not enough to explain diversity of macrophages. In this study, we analyzed the functions of macrophages induced by simultaneous stimulation with LPS and IL-4 (termed LPS/IL-4-induced macrophages). LPS/IL-4-induced macrophages were a homogeneous population showing a mixture of the characteristics of M1 and M2 macrophages. In LPS/IL-4-induced macrophages, expression of cell-surface M1 markers (I-Ab) was higher than in M1 macrophages, but lower expression of iNOS, and expression of M1-associated genes (Tnfα and Il12p40) were decreased in comparison to expression in M1 macrophages. Conversely, expression of the cell-surface M2 marker CD206 was lower on LPS/IL-4-induced macrophages than on M2 macrophages and expression of M2-associated genes (Arg1, Chi3l3, and Fizz1) varied, with Arg1 being greater than, Fizz1 being lower than, and Chi3l3 being comparable to that in M2 macrophages. Glycolysis-dependent phagocytic activity of LPS/IL-4-induced macrophages was strongly enhanced as was that of M1 macrophages; however, the energy metabolism of LPS/IL-4-induced macrophages, such as activation state of glycolytic and oxidative phosphorylation, was quite different from that of M1 or M2 macrophages. These results indicate that the macrophages induced by LPS and IL-4 had unique properties.

A Myeloid-Specific Lack of IL-4Rα Prevents the Development of Alternatively Activated Macrophages and Enhances Immunity to Experimental Cysticercosis

“…Our first observation analyzing the expression of M1 and M2 activation markers is that a mixed profile is present during T. crassiceps infection in the absence of IL-4 because increased expression of iNOS, Arginase, and RElm-α was observed simultaneously. Similar mixed expression was observed with macrophages stimulated with LPS/IL-4 [27]; also, it is widely recognized that helminth infections can induce a dual M1/M2 profile [28]. We also observed mixed IL-4/IFN-γ cytokine production in splenocytes from the Cre/LoxP mice.…”

M2 Macrophages Guide Periosteal Stromal Cell Recruitment and Initiate Bone Injury Regeneration

“…Based on the above results, we confirmed that PSCs serve as stem cells and found that MØs are likely involved in the biological regulation of PSCs after cranial injury. To explore the potential regulatory role of MØs, we examined both PSCs (PRRX1) and MØs in cranial periosteal tissue at various stages before and after injury (CD11B for macrophages and CD206 for the M2 subtype [ 32 ]).…”

Microglia Negatively Regulate the Proliferation and Neuronal Differentiation of Neural Stem/Progenitor Cells Isolated from Poststroke Mouse Brains

“…Thus, we investigated whether the negative impact of MGs/MΦs on iNSPCs was a result of a shift in MGs/MΦs toward the cytotoxic M1 type. To this end, MGs/MΦs were treated with IL4, which promotes a shift toward the M2 type [ 17 ]. FACS analysis showed that the rate of CD206 + MGs/MΦs increased from 57.3% to 79.4% following IL4 treatment ( Figure 3 I).…”