Distinct mechanisms for the induction and maintenance of allograft tolerance with CTLA4-Fc treatment
Tran, H.M.; Nickerson, P.W.; Restifo, A.C.; Ivis-Woodward, M.A.; Patel, A.; Allen, R.D.; Strom, T.B.; O'Connell, P.J.
Journal of Immunology 159(5): 2232-2239
1997
ISSN/ISBN: 0022-1767 PMID: 9278311 Document Number: 480916
A murine CTLA4/Fc gamma2a heavy chain (mCTLA4-Fc) chimeric fusion molecule was used in B6AF1 recipients of BALB/c pancreatic islet allografts to study the induction and maintenance of tolerance following inhibition of the CD28-B7 pathway for T cell activation. Donor-specific tolerance was achieved by administering 100 microg of mCTLA4-Fc on alternate days for 14 days (8 total doses) or a single 500 microg dose of mCTLA4-Fc on day 2 after transplant. Tolerance was mediated by long-lived peripheral lymphocytes and showed features of organ and alloantigen specificity. Whereas tolerance could not be established in allograft recipients receiving simultaneous mCTLA4-Fc and rIL-2, previously tolerant animals did not reject their grafts when given IL-2, suggesting that the induction and maintenance phases of tolerance were distinct and separate. The maintenance of donor-specific tolerance was an active immunologic process that was CD4+ T cell dependent and could be adoptively transferred to naive lymphocytes, but could not be explained by apoptosis or deletion of alloreactive T cells. Although an IL-2-sensitive mechanism such as anergy may contribute toward the induction of tolerance, its maintenance involves active suppression.