THE KINETICS OF MHC CLASS-I AND CLASS-II EXPRESSION IN RAT RENAL-ALLOGRAFTS - IN-VIVO LOCALIZATION WITH RADIOLABELED ANTIBODIES

We have used in vivo localization of radiolabeled antibodies in a rat renal transplant model to compare the level of induction of major hist ocompatibility complex (MHC) class I and class II molecules in grafts undergoing rejection with grafts in which rejection was modified by cy closporine (CsA). MHC class II expression increased in rejecting graft s, peaking on day 4, whereas a later rise in CsA-treated grafts was no ted. The use of donor-specific antibodies demonstrated that this was d ue, in part, to a rise in class II of donor origin. No major differenc es in MHC class I levels were noted between the two groups until after day 4, when very little antibody localization was seen in the rejecti ng group. Our results suggest that therapeutic doses of CsA. may not p revent the upregulation of class II that occurs during rejection, and that levels of class II are not of prognostic value in kidney transpla ntation.