Mechanism of acquired thymic tolerance induced by a single major histocompatibility complex class I peptide with the dominant epitope: differential analysis of regulatory cytokines in the lymphoid and intragraft compartments.
BACKGROUND
We have recently shown that intrathymic injection of a combination of immunogenic WAG-derived or Wistar-Furth (WF) (RT1.Au) major histocompatibility complex class I peptides induces acquired systemic tolerance to cardiac and islet allografts in the WF-to-ACI rat combination and therefore hypothesized that identification of the class I peptide dominance may play an important role in the induction of antigen (Ag)-specific tolerance. This study defined the peptide with the dominant epitope among the seven synthetic RT1.Au peptides and analyzed the immunoregulatory cytokines within the lymphoid and intragraft compartments associated with acquired thymic tolerance.


METHODS
ACI recipients were pretreated with intrathymic (IT) injection of 300 microg of the individual seven RT1.Au peptides 7 days before WF or Lewis cardiac transplantation. Cytokine profile of mixed lymphocyte reaction supernatants of T cells obtained from the thymus, mesenteric lymph nodes, spleen, peripheral blood leukocytes, and graft infiltrating cells after donor (WF) or third-party (Lewis) Ag stimulation were measured by enzyme-linked immunosorbent assay, whereas cytokine gene expression was determined by reverse transcription-polymerase chain reaction.


RESULTS
Only IT injection of peptide 5 (93-109) among the seven RT1.Au peptides induced donor-spe cific tolerance to cardiac allografts in the WF-to-ACI rat combination. In addition, intravenous injection of peptide 5 did not prolong WF graft survival in ACI recipients. Analysis of cytokine production by the tolerant recipients showed significant Ag-specific reduction in the production of interleukin (IL)-2 and interferon-gamma (IFN-gamma) in the thymus, mesenteric lymph nodes, spleen, and peripheral blood leukocytes, which was not associated with a concomitant Ag-specific increase in IL-4 and IL-10 production. Measurement of cytokine mRNA expression confirmed undetectable
Oluwole
S F
SF
Department of Surgery, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA.
Chowdhury
N C
NC
Ingram
M
M
Garrovillo
M
M
Jin
M X
MX
Agrawal
S
S
D000818:Animals; D016207:Cytokines / Q000502:physiology; D015536:Down-Regulation; D015870:Gene Expression; D006084:Graft Rejection / Q000235:genetics; D006085:Graft Survival; D016027:Heart Transplantation / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000494:pharmacology*; D007108:Immune Tolerance / Q000276:immunology; D016056:Immunodominant Epitopes; D007371:Interferon-gamma / Q000235:genetics; D016753:Interleukin-10 / Q000235:genetics; D007376:Interleukin-2 / Q000235:genetics; D015847:Interleukin-4 / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011912:Rats, Inbred ACI; D011917:Rats, Inbred Lew; D011920:Rats, Inbred WF; D018417:Th1 Cells / Q000378:metabolism; D018418:Th2 Cells / Q000378:metabolism; D013950:Thymus Gland / Q000276:immunology*
D016207:Cytokines; D015395:Histocompatibility Antigens Class I; D016056:Immunodominant Epitopes; D007376:Interleukin-2; D012333:RNA, Messenger; D016753:Interleukin-10; D015847:Interleukin-4; D007371:Interferon-gamma