About this Research Topic
Monocytes originate from bone marrow hematopoietic stem cells and circulate in the bloodstream. Monocytes are composed of 2 main subsets: Ly6Chigh and Ly6Clow monocytes in mice; CD14+ and CD16+ monocytes in humans. Ly6Chigh and CD14+ monocytes are termed classical monocytes and are also referred to as “inflammatory” monocytes. Although classical monocytes constitutively enter tissue in steady-state conditions, upon inflammation, they rapidly extravasate and, depending on the needs of the environment, can differentiate into multiple cell types such as monocyte-derived macrophages or dendritic cells. By contrast, the Ly6Clow and CD16+ monocytes mainly display an intra-vascular function, interacting dynamically with endothelial cells.
Monocyte extravasation and differentiation serve multiple immune functions. The differentiation of monocytes in tissue-associated macrophages at steady state can serve homeostatic functions. Monocytes can fuel acute inflammatory reactions and anti-microbial immunity by differentiating into inflammatory macrophages. Finally, monocytes also actively contribute to the resolution of inflammation and tissue regeneration.
The subset classification of monocytes is a rapidly emerging field. Recent progress in single-cell genomics and high dimensional approaches in phenotyping have highlighted additional subsets of monocytes. Monocyte heterogeneity might also adopt new dynamic transcriptional states associated with inflammation. This brings the research community to face a significant challenge of ascribing monocyte heterogeneity to specific functions. The goal of this Research Topic is to provide an editorial space that gathers contributions bringing new insights into:
i) The cellular and molecular mechanisms underlying the establishment of monocyte heterogeneity.
ii) Heterogeneity versus plasticity in monocyte terminal differentiation.
iii) The functional significance of monocyte heterogeneity at homeostasis and in infections, inflammatory conditions, and cancer.
In this Research Topic, we welcome the submission of Original Research, Methods, Protocols, Classification, Reviews, Mini-Reviews, Perspective and Clinical Trial articles that cover recent advances in the following topics:
1. Advanced characterization of monocyte heterogeneity and high dimensional approaches.
2. Monocyte ontogeny.
3. Transcriptional regulation of monocyte subsets.
4. Differentiation pathways of monocyte into steady-state tissue macrophages.
5. Monocyte diversity and antigen-presenting function.
6. Monocyte diversity in chronic inflammatory diseases.
7. Monocyte diversity and metabolism.
8. Monocyte diversity in fibrosis.
9. Monocyte diversity in cancer.
10. Monocyte infiltration and the tumor microenvironment.
11. Monocyte diversity, inflammation resolution, and tissue regeneration.
12. Therapeutic targeting of monocytes subsets in cancer, chronic inflammatory diseases and fibrosis.
13. Subset-specific features of the phagocytic pathway in monocytes populations.
14. Mouse models to study monocyte function.
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.