Lethal graft-versus-host disease across minor histocompatibility barriers in mice

Recognition of allo-peptide is governed by novel anchor imposition and limited variations in TCR contact residues

Immune specificity of a T cell is determined by the TCR contact residues exposed on the antigenic peptide/MHC complex. Naturally processed, biallelic epitopes from H7 minor histocompatibility (mH) antigen vary in position 7 (p7) from aspartic acid (D) to a glutamic acid (E), which differ by an additional methylene (-CH(2)) in the side chain. Here, we show that this variation generates a strong anti-H7a or anti-H7b cytotoxic T cell responses. Further, the H7 allelic peptides use p6 asparagine as their central anchor residue and amino acid variations in either the canonical p5 or the predicted p6 anchor positions in the antigenic epitope were detrimental for TCR recognition. In addition, introduction of any other amino acids, except asparagine, in the polymorphic p7 significantly abolished the ability of anti-H7b TCR recognition. This demonstrates that only an asparagine with an amine group as a side chain instead of a charged oxygen radical could effectively stimulate the anti-H7b specific T cells. Our findings provide evidence that mH antigen-specific TCRs are highly stringent in recognizing their cognate epitopes.

Graft-versus-host disease: How to translate new insights into new therapeutic strategies

Graft-versus-host disease occurs when transplanted donor-derived T lymphocytes recognize major or minor histocompatibility complex proteins and their associated peptides expressed by recipient antigen-presenting cells. A widely accepted paradigm for the pathophysiology of acute GVHD is based on the existence of 3 sequential steps: (1) injury to the host environment (as would occur during conditioning regimens); (2) donor T-cell activation, proliferation, and differentiation; and (3) damage to the target tissue caused by either cytotoxicity or indirectly by inflammatory cytokines. In order to reduce the incidence of GVHD, recent studies have focused on methods of prophylaxis as well as novel treatments for established GVHD. We review each phase in the development of acute GVHD and discuss recently developed interventions aimed to prevent or treat GVHD by interfering with these pathways.

Customized molecular phenotyping by quantitative gene expression and pattern recognition analysis

Description of the molecular phenotypes of pathobiological processes in vivo is a pressing need in genomic biology. We have implemented a high-throughput real-time PCR strategy to establish quantitative expression profiles of a customized set of target genes. It enables rapid, reproducible data acquisition from limited quantities of RNA, permitting serial sampling of mouse blood during disease progression. We developed an easy to use statistical algorithm--Global Pattern Recognition--to readily identify genes whose expression has changed significantly from healthy baseline profiles. This approach provides unique molecular signatures for rheumatoid arthritis, systemic lupus erythematosus, and graft versus host disease, and can also be applied to defining the molecular phenotype of a variety of other normal and pathological processes.

Adoptive immunotherapy against kidney targets in dog-leukocyte antigen-identical mixed hematopoietic canine chimeras

BACKGROUND

Stable mixed-donor-host-hematopoietic chimerism can serve as a platform for adoptive immunotherapy. Infusions of donor lymphocytes (DLI) sensitized against hematopoietic cells converted mixed hematopoietic into full-donor chimerism in dog-leukocyte antigen (DLA)-identical littermates. Whether sensitization against tissue of solid organs leads to organ-specific immunity that can be transferred by DLI was unknown and was investigated in these experiments using the kidney as target.

METHODS

DLA-identical recipients with established stable mixed-donor-host-hematopoietic chimerism were used. In five pairs, hematopoietic stem-cell transplant (HSCT) donors were sensitized by kidney transplantation from the respective chimeras. In a second group, five HSCT donors received vaccinations that were generated from kidney cells of the respective mixed chimeras. Twenty-eight days after sensitization, DLI were administered to the mixed-hematopoietic chimeras.

RESULTS

All HSCT donors rejected their kidney grafts from their mixed-chimeric recipients within 22 to 45 days. DLI caused no sustained graft-versus-kidney effects in the mixed-chimeric recipients. However, DLI donors sensitized by kidney transplantation converted 4 of 5 mixed chimeras into virtually complete (>95%) donor-type chimeras, compared with 1 of 5 mixed chimeras given DLI by vaccination from sensitized donors.

CONCLUSION

Although DLA-identical kidney grafts from mixed-hematopoietic chimeras were readily rejected by their HSCT donors, subsequent transfusions of sensitized-donor lymphocytes into mixed chimeras converted mixed to all-donor chimerism but failed to induce graft-versus-kidney effects. Vaccination strategies in lieu of kidney grafts failed to convert mixed chimerism.

Graft-versus-host-related immunosuppression is induced in mixed chimeras by alloresponses against either host or donor lymphohematopoietic cells

Graft-vs.-host (GVH)-related immunosuppression has previously been demonstrated in F1 rodent recipients of parental lymphoid cells, and has been thought to result from an immunologic attack of the donor against the host. Since all cells of such F1 recipients could potentially bear target class I MHC alloantigens, it has not previously been possible to determine precisely the target tissues responsible for development of GVH-related effects. In the present studies we have used mixed allogeneic chimeras as recipients of host or donor-strain lymphocyte inocula, and have made the surprising observation that "GVH-induced" immune unresponsiveness does not require GVH reactivity, per se, but develops in the presence of a one-way alloresponse against lymphohematopoietic cells in either the GVH or the host-versus-graft direction.

Histological changes of bile duct in experimental graft-versus-host disease across minor histocompatibility barriers. I. Light microscopic and immunocytochemical observations

Graft-versus-host disease (GVHD) across minor histocompatibility antigens was developed in mice and the bile duct lesions were surveyed for up to 7.5 months after spleen and bone marrow cell transplantation. Lymphoid cell infiltration was evident by day 3, reached maximum at 2 weeks, then reduced gradually and persisted during the observation period. Fibrous expansion of the portal tracts paralleled with the time after transplantation, but none of the cases progressed into liver cirrhosis. The infiltrates abutted the interlobular and septal bile ducts and distorted their appearance with a frequent infiltration of mononuclear lymphoid cells into the duct epithelial layer. The duct epithelium showed a variety of degenerative and hyperplastic changes, including nuclear enlargement with anisonucleosis, nuclear pyknosis, cytoplasmic and nuclear darkness, cytoplasmic vacuolization, focal epithelial dropout, formation of apoptotic bodies, and micropapillary infolding. Disappearance of the bile ducts and formation of granuloma around the bile ducts were not seen. Immunocytochemical study revealed the exclusive preponderance of helper/inducer T cells in the portal infiltrates and marked expression of I-A antigen on the bile duct epithelium in GVHD mice. These results suggest that immunological mechanisms by helper/inducer T cells against minor histocompatibility antigen on bile duct epithelium in association with class II molecules of MHC are important in the pathogenesis of the bile duct lesions. A putative role of such lymphocytes is discussed.

Thy-1 is a differentiation antigen that characterizes immature murine erythroid and myeloid hematopoietic progenitors

To determine the role of Thy-1 antigen in murine hematopoietic differentiation, bone marrow was treated with anti-Thy-1.2 antibody and complement or complement alone. Growth of immature hematopoietic progenitors, erythroid burst-forming units (BFU-E), and granulocyte/macrophage colony-forming units (CFU-GM) was greatly reduced following antibody and complement treatment and was not restored by mitogen-stimulated spleen cell supernatants. In contrast, more mature erythroid and myeloid progenitors, the erythroid colony-forming unit (CFU-E) and the macrophage progenitor stimulated by L-cell-conditioned media (LCM), were spared by anti-Thy-1.2 antibody and complement treatment. Here, to separate the effects of anti-Thy-1.2 antibody treatment on accessory cells from those on progenitors, splenic T cells and thymocytes were added to treated marrow at ratios of up to 200%. Growth of BFU-E and CFU-GM was not restored. To more precisely replace required accessory cells, male complement-treated marrow was cocultured with female anti-Thy-1.2 antibody and complement-treated marrow. Even marrow cells failed to restore female BFU-E and CFU-GM growth. Fluorescent-activated cell sorting (FACS) and immune sheep red cell rosetting with anti-Thy-1.2-labeled marrow were then performed to determine if immature hematopoietic progenitors bear Thy-1.2. These techniques revealed enrichment of BFU-E and CFU-GM in the Thy-1.2-positive fraction, demonstrating the presence of Thy-1.2 on early murine hematopoietic progenitors. CFU-E and CFU-M were present in the Thy-1.2-negative fraction following FACS separation. These data demonstrate that Thy-1.2 is a differentiation antigen, present on at least some murine BFU-E and CFU-GM and lost as they mature to CFU-E and CFU-M.