Graft Versus Host Disease (GVHD) is a clinical condition that occurs when
immune cells from a transplanted donor graft (such as bone marrow or stem cells) recognize the recipient's tissues as foreign and initiate an immune response against them. This phenomenon is particularly common in
allogeneic transplants, where the donor and recipient are genetically different.
Histological Features of GVHD
GVHD primarily affects the skin, liver, and gastrointestinal tract. Histologically, GVHD can be identified by specific changes in these tissues:
Skin
In the skin, acute GVHD is characterized by the presence of apoptotic keratinocytes in the
epidermis. The epidermal layer may also show vacuolar changes in the basal keratinocytes, and there can be a perivascular lymphocytic infiltrate in the
dermis. Chronic GVHD may lead to fibrosis and lichen planus-like changes.
Liver
Liver involvement in GVHD includes the presence of lymphocytic infiltrates in the
portal tracts and damage to the bile ducts. This can lead to cholestasis and increased levels of liver enzymes.
Gastrointestinal Tract
The gastrointestinal tract often shows crypt apoptosis, crypt loss, and lymphocytic infiltrates in the lamina propria. In severe cases, there can be extensive ulceration and loss of epithelial cells.
Pathophysiology of GVHD
The pathophysiology of GVHD involves several stages:
Initiation: The conditioning regimen (chemotherapy or radiation) damages the recipient's tissues, which releases inflammatory cytokines.
Donor T-cell Activation: Donor-derived
T cells recognize the recipient's antigens as foreign, which activates these T cells.
Effector Phase: Activated T cells proliferate and release cytokines that recruit other immune cells, leading to tissue damage.
Diagnosis of GVHD
The diagnosis of GVHD is based on clinical symptoms, histological examination, and laboratory tests.
Biopsies of affected tissues are often performed to confirm the diagnosis. Histological examination is crucial for identifying the characteristic features of GVHD in different organs.
Treatment Options
Treatment of GVHD involves immunosuppressive therapies to control the donor immune response. Commonly used drugs include corticosteroids,
calcineurin inhibitors, and monoclonal antibodies. In severe cases, additional therapies such as extracorporeal photopheresis may be required.
Prognosis and Complications
The prognosis of GVHD varies depending on the severity and the organs involved. Chronic GVHD can lead to long-term complications such as
fibrosis and secondary infections due to prolonged immunosuppression. Early diagnosis and prompt treatment are essential for improving outcomes.
Conclusion
GVHD is a complex condition that requires a multidisciplinary approach for diagnosis and management. Histological examination plays a critical role in identifying the characteristic changes in affected tissues and guiding appropriate treatment strategies. Ongoing research aims to improve our understanding of GVHD and develop more effective therapies.
