Characterization of the immunosuppressive effects of nitric oxide in graft vs host disease.
The generation of nitric oxide (.N = O) during in vitro assays involving lymphocyte-macrophage interaction can result in profound inhibition of lymphocyte proliferation. The present study examined whether .N = O synthesis plays a role in the suppression observed in immune function assays during graft vs host disease (GvHD). By using a parent to F1 model to induce GvHD (C57BL/6J to C57BL/6J x DBA 2J F1), a mild but transient increase in serum NO2- plus NO3- levels was observed on day 12 after inoculation. Resident peritoneal macrophages obtained from mice with GvHD demonstrated enhanced .N = O synthesis in response to LPS, compared with control F1 peritoneal macrophages. Similarly, when splenocytes from GvHD mice were cultured with Con A or LPS enhanced supernatant NO2- levels were observed, compared with control F1 mice. Addition of NG-monomethyl-L-arginine (NMA), a competitive inhibitor of .N = O synthesis, resulted in decreased NO2- levels and greatly enhanced proliferation in response to Con A. Addition of NMA to LPS-stimulated cultures did not enhance proliferation, perhaps as the result of the paucity of B cells in the GvHD population. LPS-induced .N = O synthesis by GvHD splenocytes was blocked by anti-IFN-gamma mAb, whereas Con A-induced .N = O synthesis was relatively unaffected by similar concentrations of anti-IFN-gamma mAb, suggesting different mechanisms of induction of .N = O synthesis. A proliferative response of splenocytes from mice with GvHD to third-party alloantigen was not detectable, even in the presence of NMA. The suppression observed when splenocytes from GvHD animals were added to control TNP-modified self cultures was partially reversed in the presence of NMA. These results demonstrate that .N = O synthesis in both splenocyte and peritoneal macrophage populations from GvHD mice is enhanced, revealing that in vivo priming of macrophages for .N = O synthesis occurs during GvHD. Some, but not all, in vitro tests of immune function by using GvHD splenocytes are suppressed by the generation of .N = O.
Hoffman
R A
RA
Department of Surgery, University of Pittsburgh, PA 15261.
Langrehr
J M
JM
Wren
S M
SM
Dull
K E
KE
Ildstad
S T
ST
McCarthy
S A
SA
Simmons
R L
RL
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D003208:Concanavalin A / Q000494:pharmacology; D005260:Female; D006086:Graft vs Host Disease / Q000276:immunology*; D007108:Immune Tolerance; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D009573:Nitrites / Q000378:metabolism; D010529:Peritoneal Cavity / Q000166:cytology; D014301:Trinitrobenzenes / Q000276:immunology; D019323:omega-N-Methylarginine
D008070:Lipopolysaccharides; D009566:Nitrates; D009573:Nitrites; D014301:Trinitrobenzenes; D003208:Concanavalin A; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine