Monocytes and Macrophages

Tissue homeostasis and remodelling

Macrophages perform this through functions such as: Angiogenesis, ECM remodelling, Efferocytosis, EMT, Epithelial cell plasticity

Antimicrobial properties of macrophages

Phagocytosis, producing ROS and RNS, and producing proteases

Immunoregulatory functions of macrophages

APC, pro and anti inflammatory cytokine production, as well as chemokine production

Osteoclasts

Form of macrophages in bone that help with trophic functions. They require RANK/RANKL signalling, where too much signalling leads to osteoporosis, and too little leads to osteopetrosis.

LY6C+ monocytes

short-lived monocytes that migrate into tissue from bloodstream

LY6C- monocytes

patrol bloodstream, picking up waste debris, signal neutrophils and promote inflammation

LY6C+PU1low monocytes

perform phagocytosis in tissue, and are antimicrobial specialised

LY6C+PU1high

Act more as APC and T cell activating cells in tissue

Tissue-resident macrophages (TRM)

HSC-independent and are derived from Yolk sac or foetal liver, depending on development of foetus. They are also self-renewing and have different functions depending on where they are, e.g microglia (brain) vs Kupffer cells (liver)

P.U.1

A transcription factor (TF) that regulates CSF1/CSF1R expression which determines macrophage role

Macrophage niche

Concept that macrophages are surrounded by specific ‘niche’ cells that help them survive by providing growth factors and anchoring. In turn, the macrophages protect them