['To determine the effect of systemic anti-CD154 monoclonal antibody on the survival of orthotopic murine corneal transplants.', 'BALB/c mice were used as recipients of syngeneic, multiple minor histocompatability (H)-disparate, or major histocompatibility complex MHC-mismatched corneal transplants. Recipient beds were either avascular (normal risk) or neovascularized (high risk). Mice were randomized to receive either anti-CD154 antibody or control immunoglobulin by intraperitoneal injection at surgery and once weekly after surgery. After orthotopic corneal transplantation, all grafts were evaluated for signs of rejection by slit lamp biomicroscopy over 8 weeks. The high-risk transplants were continuously observed until week 18 after the therapy was discontinued at week 8. Allospecific delayed-type hypersensitivity (DTH) was evaluated after transplantation in high-risk graft recipients. Frequency of interferon (IFN)-gamma-secreting T cells in the hosts was measured by enzyme-linked immunospot (ELISPOT) assay.', 'In normal-risk transplantation, the 8-week survival rate improved from 25% in control mice to 88% in anti-CD154-treated hosts of minor H-disparate grafts (P = 0.0087) and from 78% in control mice to 100% in anti-CD154-treated recipients of MHC-mismatched transplants (P = 0.177). Of particular significance, in high-risk transplantation, anti-CD154 therapy dramatically enhanced the survival of both minor H- and MHC-disparate corneal transplants to 100% (P = 0.0001) and 92% (P = 0.0002), respectively. In addition, the anti-CD154-treated mice did not exhibit allospecific immunity. However, termination of anti-CD154 led to some loss in graft survival, especially among high-risk minor H-disparate grafts. The frequency of IFN-gamma-producing T cells was significantly reduced in anti-CD154-treated hosts.'] Does blockade of CD40-CD154 costimulatory pathway promote survival of allogeneic corneal transplants?