Analysis of parathyroid graft rejection suggests alloantigen-specific production of nitric oxide by iNOS-positive intragraft macrophages.
BACKGROUND
During acute rejection of organ or tissue allografts T cells and macrophages are dominant infiltrating cells. CD4-positive T cells are important for the induction of allograft rejection and macrophages are important effector cells mediating cytotoxicity via production of nitric oxide (NO) by the inducible NO-synthase (iNOS). In the present study we analysed whether the destruction of primarily nonvascularised parathyroid allografts is also mediated by iNOS-positive macrophages.


METHODS
Hypocalcaemic Lewis rats received parathyroid isografts (from Lewis donors) and allografts (from Wistar Furth donors), respectively, under the kidney capsule. Levels of serum calcium above 2 mmol/L correlated with normal parathyroid function and below 2 mmol/L with parathyroid rejection. Accelerated parathyroid allograft rejection was induced by immunisation of Lewis recipients with the allogeneic peptide P1.


RESULTS
Determination of serum calcium levels is a useful parameter to control parathyroid graft function, and therefore to determine allograft rejection. Macrophages positive for both major histocompatibility complex (MHC) class II molecules and costimulatory molecules accumulated in iso- and allografts, but iNOS-positive macrophages were only detectable in allografts in the presence of activated CD4-positive T cells. These results confirm a cooperation between activated T cells and intragraft macrophages to induce macrophage iNOS expression. Recipients immunised with the allogeneic peptide P1 demonstrated accelerated rejection of allografts (mean+/-SD: 9.2+/-0.9 days) in contrast to nonimmunised animals (mean+/-SD: 15.8+/-1.8 days). Allografts of P1-immunised animals were infiltrated faster by activated CD4-positve T cells and, in addition, the infiltrates of iNOS-positive macrophages were stronger than those in allografts of nonimmunised animals.


CONCLUSIONS
Intragraft iNOS-positive macrophages seem to be able to produce cytotoxic NO involved in the killing of allogeneic cells during the alloimmune response against primarily nonvascularised parathyroid organ grafts. Infiltrates of iNOS-negative macrophages found in parathyroid isografts were caused by antigen-independent inflammation triggered by surgically induced injury. The absence of activated T cells in isografts and their presence in allografts underlines their importance in inducing macrophage iNOS expression.
Matuschek
Anja
A
Experimental Surgery, Experimental Transplantation Immunology, Clinic of General, Visceral, Vascular, and Paediatric Surgery (Surgical Clinic I), University of Würzburg Hospital, Würzburg, Germany. matuschek_a@chirurgie.uni-wuerzburg.dee
Ulbrich
Michael
M
Timm
Stephan
S
Schneider
Manuela
M
Thomas Germer
Christoph
C
Ulrichs
Karin
K
Otto
Christoph
C
D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000097:blood; D002450:Cell Communication; D002465:Cell Movement / Q000276:immunology; D018450:Disease Progression; D004789:Enzyme Activation / Q000276:immunology; D005786:Gene Expression Regulation; D006084:Graft Rejection / Q000097:blood / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D006649:Histocompatibility Antigens / Q000276:immunology / Q000378:metabolism; D007114:Immunization; D008213:Lymphocyte Activation; D008262:Macrophage Activation / Q000276:immunology; D017737:Macrophages, Peritoneal / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D008297:Male; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D011920:Rats, Inbred WF; D013961:Thyroid Gland / Q000201:enzymology* / Q000276:immunology / Q000473:pathology / Q000637:transplantation*; D014184:Transplantation, Homologous
D000943:Antigens, Differentiation; D006649:Histocompatibility Antigens; D010446:Peptide Fragments; C038353:histocompatibility antigens RT, rat; D052247:Nitric Oxide Synthase Type II; D002118:Calcium