Diarrhea initially is watery, but may progress to become bloody, and may require frequent blood transfusions and cause difficulty in maintaining adequate fluid balance. Diarrhea is secretory and continues despite fasting. GI symptoms most commonly include diarrhea and abdominal pain, but mucositis, mucosal ulceration, nausea, and vomiting can also occur. In severe GVHD, bullous lesions with toxic epidermal necrolysis mimicking TEN can develop. It can spread diffusely and become confluent. The most common skin manifestation is a pruritic or painful maculopapular rash that initially involves the palms, soles shoulders, and nape of the neck. It may also result in decreased responsiveness to active immunization. It can also involve the lungs, kidneys, eyes, and hematopoietic system. Īcute GVHD usually involves the skin, gastrointestinal tract, and liver, and is seen in 70%, 74%, and 44%, respectively. Donor allograft T-cells are the main effector cells for GvHD and its pathogenesis can be divided into three phases (Figure 1). Immune cells in the graft recognize the MHC proteins of the recipient tissue as "non-self" and triggers an immune response between the donor and the recipient.ĭonor cytotoxic CD-8 t cells recognize host tissue as foreign and proliferate to cause severe organ damage (type IV cytotoxic T cell hypersensitivity reaction). During transplantation, the donor tissue is usually obtained from a genetically different individual known as an "allograft". The histocompatibility genes code for MHC class I proteins that are present on all nucleated cells in the body and MHC class II molecules that are expressed only on antigen-presenting cells. The ability to recognize "non-self" cells depends on a set of genes knows as the histocompatibility genes that provide instructions for making a group of related proteins known as major histocompatibility complex (MHC proteins) or human leukocyte antigens (HLA). ![]() ![]() Cells of the immune system are trained early to differentiate between "self" cells and "non-self" cells.
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