MHC antigen expression in parathyroid tissue and its influence on graft sur
vival after allogeneic transplantation were investigated using a heterotopi
c rat transplantation model. MHC class I and II expression in parathyroid t
issue of Lewis (LEW), Dark Agouti (DA), and Wistar-Furth (WF) rats was anal
ysed semi-quantitatively by using immunohistochemistry. MHC class I express
ion was strong in DA, moderate in WF, and weak in LEW rats parenchyma, wher
eas MHC class II expression was negative. In the interstitium of all invest
igated tissue specimens, the proportion of MHC class II-expressing cells wa
s low. Additionally, four groups were transplanted: 1) LEW to LEW, 2) DA to
DA, 3) LEW to DA, and 4) WF to LEW. After syngeneic transplantation, graft
survival could be documented over the whole observation period. A median g
raft survival of 20 (+/-2) days was observed after transplantation from LEW
to DA, whereas grafts in the group WF to LEW were rejected after 13 (+/-1)
days. The number of intra-graft leucocytes expressing MHC class II molecul
es was the same in all groups, whereas increased levels of MHC class I in p
arathyroid tissue before transplantation resulted in a more rapid rejection
. These results indicate that immunogenicity of rat parathyroid tissue migh
t be determined by the amount of MHC class I expressed in donor parenchymal
cells. Further experiments are necessary to validate this observation. (C)
2001 Wiley-Liss, Inc.