Graft vs Host Disease
| Overview |
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- Graft vs Host Disease (GVHD) is a pattern of transplant rejection in which donor immune cells mount an immune response against host tissues.
| Etiologies |
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- Overview
- GVHD occurs when significant numbers of functional donor T-cells are directly engrafted into a recipient or if donor T-cells can develop from engrafted Hematopoietic Stem Cells. GVHD is much more common in immunocompromised recipients and this is frequently the case in the context of bone marrow or solid organ transplantation in which the immune system of patients is iatrogenically suppressed by pharmaceuticals.
- Common Clinical Scenarios
- Bone Marrow Transplantation: Donor T-cells develop from engrafted Hematopoietic Stem Cells
- Liver Transplantation: Livers are rich in lymphoid cells, including T-cell]s
- Blood Transfusion: This only occurs if transfused blood is not properly irradiated to kill circulating donor T-cells
| Pathogenesis |
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- It is thought that the pathogenesis of GVHD is essentially due to a Type IV Hypersensitivity reaction mounted by donor T-cells against host tissues. Donor T-cells are thought to mistake presentation of self-peptide:MHC I complexes on host cells with presentation of microbial-peptide:MHC I complexes. Consequently, donor T-cells will mount a Cell-mediated Immune Response against host tissues. Both donor CD8+ T-cells and donor CD4+ T-cell]]s are thought to be activated, resulting in the development of both T-cell-mediated Cytotoxicity and Delayed-type Hypersensitivity aspects of Type IV Hypersensitivity.
| Clinical Consequences |
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- Overview
- The principle target of donor T-cells appears to be host epithelial tissues. Symptomology lasting less than three months is termed "Acute GVHD" while that lasting more than three months is termed "Chronic GVHD".
- Symptomology
- Liver: Bile duct epithelium is damaged leading to cholestasis and ultimately jaundice
- Skin: Generalized maculopapular skin rash
- GI System: GI Mucosa damaged leading to diarrhea