Effect of lung surfactant collectins on bronchoalveolar macrophage interaction with Blastomyces dermatitidis: inhibition of tumor necrosis factor alpha production by surfactant protein D.
Alveolar surfactant modulates the antimicrobial function of bronchoalveolar macrophages (BAM). Little is known about the effect of surfactant-associated proteins in bronchoalveolar lavage fluid (BALF) on the interaction of BAM and Blastomyces dermatitidis. We investigated BALF enhancement or inhibition of TNF-alpha production by BAM stimulated by B. dermatitidis. BAM from CD-1 mice were stimulated with B. dermatitidis without or with normal BALF, surfactant protein A-deficient (SP-A-/-) or surfactant protein D-deficient (SP-D-/-) BALF, or a mixture of SP-A-/- and SP-D-/- BALF. An enzyme-linked immunosorbent assay was used to measure tumor necrosis factor alpha (TNF-alpha) in culture supernatants. BALFs were standardized in protein concentration. BAM plus B. dermatitidis (BAM-B. dermatitidis) TNF-alpha production was inhibited > or = 47% by BALF or SP-A-/- BALF (at 290 or 580 microg of protein/ml, P < 0.05 to 0.01); in contrast, SP-D-/- BALF did not significantly inhibit TNF-alpha production. If SP-A-/- BALF was mixed in equal amounts with SP-D-/- BALF, TNF-alpha production by BAM-B. dermatitidis was inhibited (P < 0.01). Finally, pure SP-D added to SP-D-/- BALF inhibited TNF-alpha production by BAM-B. dermatitidis (P < 0.01). B. dermatitidis incubated with BALF and washed, plus BAM, stimulated 63% less production of TNF-alpha than did unwashed B. dermatitidis (P < 0.05). SP-D was detected by anti-SP-D antibody on BALF-treated unwashed B. dermatitidis in an immunofluorescence assay (IFA). The BALF depleted by a coating of B. dermatitidis lost the ability to inhibit TNF-alpha production (P < 0.05). 1,3-beta-Glucan was a good stimulator of BAM for TNF-alpha production and was detected on B. dermatitidis by IFA. beta-Glucan incubated with BALF inhibited the binding of SP-D in BALF to B. dermatitidis as demonstrated by IFA. Our data suggest that SP-D in BALF binds beta-glucan on B. dermatitidis, blocking BAM access to beta-glucan, thereby inhibiting TNF-alpha production. Thus, whereas BALF constituents commonly mediate antimicrobial activity, B. dermatitidis may utilize BALF constituents, such as SP-D, to blunt the host defensive reaction; this effect could reduce inflammation and tissue destruction but could also promote disease.
Lekkala
Madhavi
M
Division of Infectious Diseases, Department of Medicine, Santa Clara Valley Medical Center, 751 South Bascom Ave., San Jose, California 95128-2699, USA.
LeVine
Ann Marie
AM
Linke
Michael J
MJ
Crouch
Erika C
EC
Linders
Bruce
B
Brummer
Elmer
E
Stevens
David A
DA
D000818:Animals; D001758:Blastomyces / Q000276:immunology / Q000472:pathogenicity*; D001759:Blastomycosis / Q000276:immunology / Q000382:microbiology; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology / Q000382:microbiology; D008262:Macrophage Activation; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000276:immunology*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D037663:Pulmonary Surfactant-Associated Protein D / Q000172:deficiency / Q000378:metabolism / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000187:drug effects*; D047071:beta-Glucans / Q000378:metabolism
D037663:Pulmonary Surfactant-Associated Protein D; D014409:Tumor Necrosis Factor-alpha; D047071:beta-Glucans