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MECHANISMS OF INDIRECT ALLORECOGNITION IN GRAFT REJECTION

1996; Wolters Kluwer; Volume: 62; Issue: 6 Linguagem: Inglês

10.1097/00007890-199609270-00001

1534-6080

Wanjun Chen, Barbara Murphy, Ana Maria Waaga, Theresa Willett, Mary E. Russell, Samia J. Khoury, Mohamed H. Sayegh,

Immune Response and Inflammation

Recent animal studies suggest that indirect T-cell recognition of alloantigen plays an important role in allograft rejection and tolerance. In this study, we generated T cell clones from Lewis (LEW, RT11) rat lymph node cells that had been primed in vivo by immunization with immunogenic class II MHC allopeptide RT.1Duβ2, representing residues 20-44 of the polymorphic β chain of RT1.Dβu(Wistar Furth [WF]). Using reverse transcriptase polymerase chain reaction transcript analysis with specific rat T cell receptor Vβ primers, we show that six out of nine T cell clones specifically proliferated to RT1.Duβ2 and expressed Vβ 9. One of these clones, clone 2F4, which specifically proliferated to RT1.Duβ2 in a dose-response fashion and produced interferon-γ in response to restimulation by RT1.Duβ2, was selected for further studies. The β-chains of RT1.D1and RT1.Duresidues 20-44 differ by two amino acids at positions 30 and 38. We synthesized two peptides, each containing a single polymorphic site: RT1.Duβ 20-33 and RT1.Duβ 31-44. Both these peptides were immunogenic in LEW responders, since lymph node cells primed by immunization proliferated equally to the peptides in vitro. Interestingly, in vitro dose-response studies with clone 2F4 showed better proliferative response to peptide RT1.Duβ 20-33 than to peptide RT1.Duβ 31-44, indicating that this T cell clone preferentially recognizes a single amino acid difference on residue 30. Finally, it has been suggested that indirect allorecognition by CD4+T cells mediate graft rejection by delayed-type hypersensitivity responses, although definitive studies are lacking. Systemic injection of the 2F4 clone to naive LEW rats elicited an antigen-specific delayed-type hypersensitivity response against RT1.Duβ2 peptide and WF splenocytes, confirming indirect presentation in vivo. These data demonstrate that Th1 cell clones generated by in vivo priming via the indirect pathway utilize specific T cell receptor Vβ and recognize single amino acid differences in the allopeptide. More importantly, these Th1 clones are capable of mediating a specific immune response in vivo. These studies with MHC allopeptide-specific T cell clones further delineate the cellular mechanisms of indirect allorecognition and provide a potential strategy to study its role in acute and chronic rejection, and tolerance.