Abstract
CD5L (CD5 molecule-like) is a secreted glycoprotein that controls key mechanisms in inflammatory responses, with involvement in processes such as infection, atherosclerosis, and cancer. In macrophages, CD5L promotes an anti-inflammatory cytokine profile in response to TLR activation. In the present study, we questioned whether CD5L is able to influence human macrophage plasticity, and drive its polarization toward any specific phenotype. We compared CD5L-induced phenotypic and functional changes to those caused by IFN/LPS, IL4, and IL10 in human monocytes. Phenotypic markers were quantified by RT-qPCR and flow cytometry, and a mathematical algorithm was built for their analysis. Moreover, we compared ROS production, phagocytic capacity, and inflammatory responses to LPS. CD5L drove cells toward a polarization similar to that induced by IL10. Furthermore, IL10- and CD5L-treated macrophages showed increased LC3-II content and colocalization with acidic compartments, thereby pointing to the enhancement of autophagy-dependent processes. Accordingly, siRNA targeting ATG7 in THP1 cells blocked CD5L-induced CD163 and Mer tyrosine kinase mRNA and efferocytosis. In these cells, gene expression profiling and validation indicated the upregulation of the transcription factor ID3 by CD5L through ATG7. In agreement, ID3 silencing reversed polarization by CD5L. Our data point to a significant contribution of CD5L-mediated autophagy to the induction of ID3 and provide the first evidence that CD5L drives macrophage polarization.
Highlights
Macrophages are innate immune cells present in all vertebrate tissues
To gain a thorough understanding of the role of CD5-like protein (CD5L) in human macrophage polarization, we examined the phenotypic and functional changes induced by this protein, when compared with the response to culture medium (−) or the standard polarization stimuli IFN/LPS, IL4, or IL10
The classification algorithm was used to compare the distances between recombinant CD5L (rCD5L)-induced surface marker levels (i median fluorescence intensity (MFI) ) CD5L,d to the three patterns of the standard stimuli (IFN/LPS, IL4, and IL10)
Summary
Macrophages are innate immune cells present in all vertebrate tissues. To ensure homeostasis, these cells respond to internal and external cues and exert trophic, regulatory, repair, and effector functions [1]. This plasticity allows them to acquire a wide range of functions, from proinflammatory, pathogeneliminating, and subsequent tissue-damaging (referred to as M1 or classically activated macrophages) to anti-inflammatory, immunosuppressive, and wound-healing (referred to as M2 or alternatively activated) [4] In this context and given the inherent plasticity of these cells, there is growing interest in applying knowledge of their polarization to treat human diseases. We adopted the macrophage nomenclature proposed by Murray et al based on the activation stimulus, i.e., M-INF/LPS, M-IL4, and M-IL10, as well as M-dexamethasone (DXM), which have been referred to as M1, M2a, and M2c, respectively [8] These macrophage subsets have been classified on the basis of their gene signatures, activation signaling pathways, surface molecule expression pattern, secretory profile, and functional properties [6, 7, 9,10,11,12]. These observations highlight the urgent need for further advancement of our knowledge of human macrophage polarization [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
