Genetic evidence of a functional monocyte dichotomy.
Human peripheral blood monocytes are found as two distinct populations based upon differential expression of chemokine receptors, adhesion molecules, Fc receptors, and cytokines. cDNA microarray analysis now reveals additional differences between these subsets that suggest dramatically diverse functions. One monocyte subset (CD14++CD16-) appears to be closely paired with neutrophils, and may have as its primary function the removal and recycling of apoptotic neutrophils at sites of inflammation. The other monocyte subset (CD14+CD16+) expresses numerous genes encoding proteins with antimicrobial activity and thus may be more directly involved in peripheral host defense. The production of monocytes capable of efficiently removing dying neutrophils may be necessary to prevent host tissue damage and autoimmune response induction. Therefore, species like humans that produce relatively high levels of circulating neutrophils must also produce relatively high numbers of the recycling monocytes. Conversely, species such as mice and rats that maintain relatively lower levels of circulating neutrophils require fewer recycling monocytes.
Mobley
James L
JL
Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105, USA. James.mobley@pfizer.com
Leininger
Michael
M
Madore
Steven
S
Baginski
Theodore J
TJ
Renkiewicz
Richard
R
D000818:Animals; D005260:Female; D005434:Flow Cytometry; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics*; D019041:L-Selectin / Q000032:analysis; D007958:Leukocyte Count; D018950:Lipopolysaccharide Receptors / Q000032:analysis; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000737:chemistry / Q000145:classification / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017452:Receptors, IgG / Q000032:analysis; D013045:Species Specificity
D018950:Lipopolysaccharide Receptors; D012333:RNA, Messenger; D017452:Receptors, IgG; D019041:L-Selectin