monocytes and macrophages

functions

clear apoptotic cells
clear pathogens
mediate tissue homeostasis and growth
vascularisation

clearing apoptotic cells

express Tim-4 and TAM apoptotic recognition receptors
recognise phosphatidyl serine
induction of SOCs1 and 3 to repress cytokine signalling

classes of monocytes

classical - CD14+CD16-
intermediate - CD14+CD16+
non classical - CD14-CD16+

experiment showing development of monocyte classes

deuterium labelling incorporates into DNA upon cell division
classical

release of monocytes from bone marrow

intermediate and non-classical not present in bone marrow

origin of macrophages

some macrophage populations are independent of the bone marrow - self maintaining
evidence - langerhans cells repopulate after BM transplant but monocytes were of donor origin
in yolk sack

macrophage subsets

M1 - induced by bacterial cell wall

role of macrophages in RA

CCL2 accumulation in synovial tissues - pro inflammatory macrophage profile
differentiate into osteoclasts responsible for bone erosion
mediated by MCSF and RANK1

monocytes in IBD

mucosa of patients enriched with immature inflammatory cytokines

monocytes in MS

inflammatory monocytes recruited to CNS by IL33 release from dead oligodendrocytes

alveolar macrophages support by epithelial cells

T1 epithelial cells carry out gas exchange
T2 epithelial cells responsible for surfactant production

alveolar macrophage functions

regulate surfactant level to decrease surface tension
clear air spaces of noxious particles
regulated through CD200R

avms in COVID

increased CCL2
infection of alveolar epithelial cells means no inhibitory ligands present so macrophages are activated
inhaled GMSF increased oxygenation