Dynamic expression of the signal regulatory protein alpha and CD18 on porcine PBMC during acute endotoxaemia.
Endotoxaemia elicits a massive inflammatory insult affecting the beta2 integrin CD18. Being an adhesion molecule, CD18 is pivotal in inflammation and, moreover, exiting data suggest that CD18 is a lipopolysaccharide (LPS) receptor. Early LPS-induced inflammation is regulated by the signal regulatory protein (SIRPalpha), which is identical to the porcine panmyelocytic marker swine CD workshop 3 (SWC3), and LPS-induced downregulation of SIRPalpha has been described in vitro. The dynamic SIRPalpha/SWC3 and CD18 expression on peripheral blood mononuclear cells (PBMC) in vivo during LPS-induced inflammation is the focus of this study. Pigs were randomized into LPS (n = 12) or control (n = 6) groups. At start 0 min, LPS infusion was stepwise (2.5-15 mug/kg/h, 30 min) followed by maintenance infusion (2.5 mug/kg/h, 330 min). PBMC were isolated at 0, 60, 240 and 360 min, and two-colour flow cytometry was performed using monoclonal antibodies identifying SWC3 and CD18. Viability was tested using 7-amino-actinomycin D. LPS dramatically changed the relative distribution of circulating myeloid cells. At 60 min monocytes disappeared. This was followed by reappearance of a distinct population with low CD18 and SIRPalpha/SWC3 expression. Cell sorting showed that the appearing population comprised band neutrophils and apoptotic/dead cells. The remaining monocytes expressed less CD18 at 360 min than the controls (P = 0.03). The appearance of a distinct cell population comprising apoptotic cells and band neutrophils consistent with LPS-induced apoptosis, and decreased CD18 expression on monocytes suggests that early CD18 downregulation is profitable for the host in a situation with an intense LPS stimulus.
Ebdrup
L
L
Department of Anaesthesiology and Intensive Care Medicine, Aarhus University Hospital, Aarhus Sygehus, DK, Denmark.
Krog
J
J
Granfeldt
A
A
Tønnesen
E
E
Hokland
M
M
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D018821:CD18 Antigens / Q000096:biosynthesis*; D015536:Down-Regulation; D019446:Endotoxemia / Q000139:chemically induced / Q000276:immunology* / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D008070:Lipopolysaccharides / Q000276:immunology* / Q000633:toxicity; D011971:Receptors, Immunologic / Q000096:biosynthesis*; D013552:Swine
D018821:CD18 Antigens; D008070:Lipopolysaccharides; D011971:Receptors, Immunologic