Cell membrane receptors on bovine mononuclear phagocytes involved in phagocytosis of Mycobacterium avium subsp paratuberculosis.
OBJECTIVE
To determine cell membrane receptors involved in phagocytosis of Mycobacterium avium subsp paratuberculosis (MAP) organisms.


METHODS
Monocytes were obtained from healthy adult Holstein dairy cows that were test negative for MAP infection on the basis of bacteriologic culture of feces and serologic test results.


METHODS
Monocytes or bovine macrophage cell line (BoMac) cells were incubated with MAP organisms for 30, 60, or 120 minutes with or without inhibitors of integrins, CD14, or mannose receptors. Phagocytosis was evaluated by light microscopy or by flow cytometry. CD11a/CD18, CD11b, and CD14 expression on monocytes and BoMac cells was evaluated by use of flow cytometry.


RESULTS
Monocytes and BoMac cells rapidly phagocytized MAP organisms. However, compared with BoMac cells, monocytes had a greater total capacity to phagocytize MAP organisms. Addition of neutralizing anti-integrin antibodies (anti-CD11a/CD18 and anti-CD11b) substantially inhibited phagocytosis by monocytes during the first 60 minutes of incubation with MAP organisms, but were less effective at 120 minutes of incubation. Anti-CD11a/CD18 and anti-CD11b antibodies were less effective in inhibiting phagocytosis by BoMac cells. Addition of inhibitors of CD14 or mannose receptors also inhibited phagocytosis of MAP by monocytes. Addition of a combination of integrin and mannose inhibitors had an additive effect in reducing phagocytosis, but addition of integrin and CD14 inhibitors did not have an additive effect.


CONCLUSIONS
Multiple receptors are involved in phagocytosis of MAP organisms. Although CD11/CD18 receptors appear to be the major receptors used by MAP at early time points, mannose receptors and CD14 also contribute substantially to phagocytosis.
Souza
Cleverson D
CD
Department of Veterinary and Biomedical Science, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108, USA.
Evanson
Oral A
OA
Sreevatsan
Srinand
S
Weiss
Douglas J
DJ
D000818:Animals; D040881:CD11a Antigen / Q000276:immunology; D039481:CD11b Antigen / Q000276:immunology; D002417:Cattle / Q000276:immunology*; D002418:Cattle Diseases / Q000276:immunology* / Q000382:microbiology; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000382:microbiology; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D016023:Integrins / Q000276:immunology; D037181:Lectins, C-Type / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000276:immunology; D009000:Monocytes; D016927:Mycobacterium avium subsp. paratuberculosis / Q000276:immunology*; D010283:Paratuberculosis / Q000276:immunology* / Q000382:microbiology; D010587:Phagocytosis / Q000276:immunology; D011956:Receptors, Cell Surface / Q000276:immunology; D011971:Receptors, Immunologic / Q000276:immunology*
D040881:CD11a Antigen; D039481:CD11b Antigen; D016023:Integrins; D037181:Lectins, C-Type; D018950:Lipopolysaccharide Receptors; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic