Evidence that nitric oxide production by in vivo allosensitized cells inhibits the development of allospecific CTL.
The oxidative metabolism of L-arginine to its bioactive product, nitric oxide (.N = O) has been shown to inhibit rat splenocyte mixed lymphocyte reactions. To determine if alloantigen-induced .N = O production might be operative in vivo, cells that had infiltrated a rat sponge matrix allograft were tested for de novo .N = O production as well as .N = O production upon restimulation with the sensitizing alloantigen. When graft-infiltrating cells were placed in culture, a peak in de novo .N = O production was observed by day 6 graft-infiltrating cells, the time when donor-specific CTL activity by the graft-infiltrating cells was first observed. Upon restimulation with alloantigen, allograft-infiltrating cells produced greatly increased levels of .N = O, and this production was associated with inhibition of lymphocyte cytolytic function. The addition of NG-monomethyl-L-arginine (NMA), the competitive inhibitor of oxidative L-arginine metabolism, inhibited .N = O production and promoted allospecific CTL development. Both observed effects of NMA were reversed by addition of excess L-arginine. Cytokine(s) able to induce proliferation of the IL-2-dependent T cell line CTLL-2 could be detected in alloantigen-stimulated cultures in both the presence and absence of NMA. However, proliferation of the graft-infiltrating cells in response to these cytokines was observed only in the presence of NMA. The immunosuppressive macrolide FK506 was a potent inhibitor of .N = O production in these cultures, presumably acting by inhibiting the production of those cytokines that induce the oxidative L-arginine pathway.
Department of Surgery, University of Pittsburgh, Pennsylvania 15261.
J M
JM
Langrehr
K E
KE
Dull
J B
JB
Ochoa
T R
TR
Billiar
S T
ST
Ildstad
W H
WH
Schraut
R L
RL
Simmons
R A
RA
Hoffman
D000818:Animals; D000937:Antigen-Antibody Reactions; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D002452:Cell Count; D002478:Cells, Cultured; D000939:Epitopes; D007519:Isoantigens / Q000276:immunology; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D051381:Rats; D011912:Rats, Inbred ACI; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D013154:Spleen / Q000166:cytology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014184:Transplantation, Homologous; D019323:omega-N-Methylarginine
D000939:Epitopes; D007519:Isoantigens; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine