Allochimeric class I MHC protein-induced tolerance by partial TCR engagement requires activation of both CTL4- and common gamma-chain-dependent cytokine signals.
BACKGROUND
The various toxicities associated with the general immune suppression resulting from current clinical immunosuppressive therapies continue to plague transplant recipients as well as jeopardize allograft survival.


METHODS
The present study utilized allochimeric class I MHC antigens (alpha1hu70-77-RT1.Aa) bearing only four donor RT1.Au polymorphic amino acids (a.a.; His70, Val73, Asn74, and Asn77) superimposed on the recipient RT1.Aa background to induce transplantation tolerance in the rat cardiac transplant model.


RESULTS
Oral delivery of alpha1hu70-77-RT1.Aa protein alone (days 0-6) induced tolerance, as evidenced by inhibition of both acute and chronic rejection processes. Delivery of alpha1hu70-77-RT1.Aa with therapeutic doses of cyclosporine (CsA) also prevented chronic rejection, otherwise readily developed after treatment with CsA alone. A polymerase chain reaction (PCR)-based analysis showed that tolerant recipients had reduced numbers of interleukin (IL)-2/interferon (IFN)-gamma-producing T helper (Th)1 cells and elevated numbers of IL-4/IL-10-producing Th2 cells. Adoptive transfer experiments revealed that potent regulatory T cells mediated tolerance. The same T cells displayed diminished T cell receptor (TCR)-driven signaling via extracellular regulated kinase, AP-1, and NF-kappaB, as well as the common gamma-chain (gammac) cytokine-receptor-induced signaling by Janus kinase 3 (Jak3)/stimulators and activators of transcription Stat/5 pathways. Tolerance induction was prevented in vivo by inhibition of signal 2 by CTL4Ig or of signal 3 by either rapamycin, which disrupts the mammalian target of rapamycin, or AG490, which inhibits Jak3. Finally, partial or complete tyrosine phosphorylation of Zap70 was observed in alloantigen-specific T cell clones in response to tolerogenic versus immunogenic peptides, respectively.


CONCLUSIONS
Tolerance induction by allochimeric proteins is achieved by partial TCR activation in the presence of signals 2 and 3, resulting in a skewed Th2 phenotype.
Stepkowski
Stanislaw M
SM
Division of Immunology and Organ Transplantation, Department of Surgery, The University of Texas Medical School at Houston, Houston, Texas 77030, USA. Stanislaw.Stepkowski@uth.tmc.edu
Kirken
Robert A
RA
Trawick
Barton W
BW
Wang
Min
M
Tejpal
Neelam
N
Wang
Mou-Er
ME
Tian
Ling
L
Clark
James
J
Kahan
Barry D
BD
D000069594:Abatacept; D019264:Adoptive Transfer; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000276:immunology*; D060908:CTLA-4 Antigen; D016207:Cytokines / Q000276:immunology*; D004359:Drug Therapy, Combination; D016027:Heart Transplantation / Q000276:immunology*; D006649:Histocompatibility Antigens / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D018796:Immunoconjugates; D007146:Immunoglobulin lambda-Chains / Q000276:immunology*; D007165:Immunosuppression Therapy / Q000379:methods; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008213:Lymphocyte Activation; D008297:Male; D016133:Polymerase Chain Reaction; D051381:Rats; D011914:Rats, Inbred BN; D011920:Rats, Inbred WF; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D018183:Transplantation Chimera; D014184:Transplantation, Homologous
D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556708:Ctla4 protein, rat; D016207:Cytokines; D006649:Histocompatibility Antigens; D015395:Histocompatibility Antigens Class I; D018796:Immunoconjugates; D007146:Immunoglobulin lambda-Chains; D007166:Immunosuppressive Agents; D011948:Receptors, Antigen, T-Cell; C038353:histocompatibility antigens RT, rat; D000069594:Abatacept