T-cell mediated responses in a murine model of orthotopic corneal transplantation.

To evaluate the role that delayed-type hypersensitivity (DTH) and cytotoxic T lymphocyte responses play in a murine model of orthotopic corneal allograft transplantation. Corneal transplantation was performed by grafting C57BL/6 donor corneas into BALB/c corneal beds. After transplantation, the mice were observed by slit lamp biomicroscopy on a weekly basis and graded for signs of graft rejection and delayed-type hypersensitivity (DTH) and cytotoxic T lymphocyte (CTL) responses to donor alloantigens assessed at selected times after grafting. It was determined that between 40% and 65% of BALB/c mice rejected C57BL/6 corneas by 8 weeks after engraftment. Mice with opacity scores > 2 demonstrated significantly greater DTH responses than did mice with opacity scores < 2 at 2, 3, and 4 weeks after engraftment. After 4 weeks, the DTH responses for all groups were essentially the same as for naive BALB/c mice. The DTH responses were specific for C57BL/6 alloantigens and are primarily directed against non-major histocompatibility complex (MHC) C57BL/6 alloantigens and are primarily directed against non-major histocompatibility complex C57BL/6 alloantigens, as evidenced by the ability of B10.D2 cells to elicit DTH responses whereas C.B10-H-2b cells did not. However, although BALB/c mice engrafted with C57BL/6 tail skin demonstrated significantly greater CTL activity than naive BALB/c mice, there was no significant difference in CTL activity between BALB/c mice whose C57BL/6 corneal allografts displayed opacity scores greater than (rejected) or less than (accepted) 2. The mechanism whereby corneal allografts in this strain combination are rejected is best associated with the ability to generate strong DTH responses and not CTL activity. This DTH response also demonstrates alloantigen specificity and appears to be primarily directed against the non-MHC component of the corneal transplant.

Joo CK ，Pepose JS ，Stuart PM 《INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE》

Antigen presentation by Langerhans cells in vivo: donor-derived Ia+ Langerhans cells are required for induction of delayed-type hypersensitivity but not for cytotoxic T lymphocyte responses to alloantigens.

Peeler JS ，Niederkorn JY 《JOURNAL OF IMMUNOLOGY》

Characterization of cell-mediated immune responses elicited by orthotopic corneal allografts in mice.

Corneal allografts placed orthotopically induce a unique and unusual response in recipient mice. More orthotopic corneal allografts are accepted indefinitely than similar skin allografts. Of the rejected corneal grafts, class I major histocompatibility complex (MHC)-incompatible grafts are rejected less frequently than grafts that express only minor histocompatibility complex (minor H) or MHC plus minor H alloantigens. To describe the spectrum of T cells activated (or not) by orthotpic corneal grafts, the authors examined the development of delayed hypersensitivity (DH) to donor-specific alloantigens. Recipient BALB/c mice received orthotopic corneal allografts from donor mice that were MHC incompatible at MHC loci only, multiple minor H loci only, or MHC plus multiple minor H loci. These groups of mice were examined to determine when alloantigen-specific DH developed. The authors report that all mice, whether they accept or reject grafts, acquire donor-specific DH within 4 weeks of engraftment. This reactivity is primarily directed at minor H, rather than MHC-encoded, alloantigens. Through time, spontaneous DH reactivity disappears in all mice, and thereafter, donor-specific DH can be induced by cognate immunization only in mice that have rejected their cornea grafts. These results can be explained in the context of "direct" and "indirect" pathways of allorecognition. Because normal corneas lack passenger leukocytes, the potential for direct recognition of alloantigens on orthotopic corneal grafts is small. Therefore, T cells activated by orthotopic corneal allografts must recognize donor-derived antigens primarily on recipient antigen presenting cells, that is, through the indirect pathway of allorecognition. Because minor H antigens are the dominant cellular proteins in grafts, it is proposed that minor H determinants are the most immunogenic alloantigens in orthotopic corneal grafts because they are the major source of peptides that will be loaded onto recipient class II molecules for T-cell recognition. We further predict that long-term acceptance of corneal allografts is promoted when recipient mice acquire anterior chamber associated immune deviation (impaired and suppressed DH) directed at minor H alloantigens of the grafts.

Sonoda Y ，Sano Y ，Ksander B ，Streilein JW ... -  《INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE》

Corneal allografts induce cytotoxic T cell but not delayed hypersensitivity responses in mice.

Peeler J ，Niederkorn J ，Matoba A 《INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE》

Preservation of donor cornea prevents corneal allograft rejection by inhibiting induction of alloimmunity.

To determine whether preservation of the donor cornea prevents allograft rejection, orthotopic corneal transplantation was performed using corneas preserved in storage medium (Optisol-GS((R))). Donor corneas harvested from C3H/He (H-2(k)) mice and B10.D2 (H-2(d)) mice were preserved in storage medium for 0, 3, 7 and 14 days, and then transplanted into the corneal beds of the recipient BALB/c (H-2(d)) mice. Graft survival was determined clinically and histologically. The expression of major histocompatibility complex (MHC) molecules in the preserved corneas was analysed by immunohistochemistry and Western blotting. Donor-specific cytotoxic T lymphocyte (CTL) and delayed-type hypersensitivity (DTH) responses were assessed 3 weeks after grafting. Active suppression of DTH in the recipient mice was also examined 3 weeks after grafting. The survival of 14 day preserved allografts was significantly higher than that of the non-preserved allografts in both MHC and minor histocompatibility (H) antigens, and minor H only disparate combination. The recipients of the preserved allografts failed to induce both CTL and DTH. The active suppression of DTH was not acquired in these recipients. The expression of donor-derived MHC class I antigens was markedly reduced in the corneas after preservation. Preservation of the donor cornea had a remarkable effect on the prevention of corneal allograft rejection. Since the preserved allografts failed to induce donor-specific CTL and DTH, and active suppression of DTH was not acquired in the recipients, the prevention of allo-rejection is due to a failure of allo-sensitization. These results indicate that the reduction of MHC class I antigens and minor H antigens expression in the preserved grafts induces a failure of allo-sensitization and leads to the high rate of acceptance in corneal allografts.

Kamiya K ，Hori J ，Kagaya F ，Usui T ，Amano S ，Oshika T ，Mizouchi T ，Tsuru T ，Yamagami S ... -  《EXPERIMENTAL EYE RESEARCH》