Medical Quiz

Overview of Organ Transplantation, Rejection, and Hematopoietic Stem Cell Transplantation

• Organ transplantation is used to treat irreversible diseases of the kidney, liver, heart, lung, and bone marrow.

• Transplant rejection occurs when the recipient's immune system recognizes the donated organ as foreign and attacks it.

• Hyperacute rejection occurs within minutes to hours due to pre-formed host antibodies reacting against graft antigens. This is now uncommon due to pre-operative testing.

• Acute rejection occurs within days to weeks and is mediated by both humoral and cell-mediated mechanisms. It is clinically characterized by renal failure and T-cell infiltration.

• Chronic rejection occurs slowly and progressively months to years after transplantation due to inadequate immune suppression therapy. It is characterized by intimal fibrosis of arteries and arterioles, leading to ischemic damage to the parenchyma.

• Hematopoietic stem cell transplantation is used as therapy for hematopoietic conditions and involves chemotherapy and/or irradiation to destroy native marrow cells and create a graft bed.

• Graft-versus-host disease (GVHD) occurs when T cells present in the graft react against the recipient's cells, causing inflammation and killing host cells.

• Better matching of the donor and the recipient improves graft survival.

• Immunosuppression is necessary in all organ transplantation, except for identical twins.

• Immunosuppressed individuals are at increased risk of opportunistic fungal, viral, and other infections, as well as autoimmune diseases and associated cancers.

• Autoimmune diseases occur due to immune reactions against self-antigens, and genetic factors play a significant role in predisposition.

• Environmental factors such as hormones, infections, drugs, and ultraviolet radiation may trigger autoimmune diseases.

• Autoimmune diseases may be organ-specific or non-organ-specific, and multi-organ involvement is frequently caused by secondary damage due to circulating immune complexes.Autoimmune Diseases and Amyloidosis

• Systemic Lupus Erythematosus (SLE) is a complex autoimmune disease caused by genetic, hormonal, and environmental factors that lead to the production of autoantibodies.

• Antinuclear antibodies (ANAs) are positive in almost every SLE patient, but the presence of autoantibodies against double-stranded DNA is diagnostic.

• Immune complexes (type III hypersensitivity) cause most of the visceral lesions, and autoantibodies against blood cells cause effects by type II hypersensitivity.

• Sjögren Syndrome is an inflammatory autoimmune disease that primarily affects the salivary and lacrimal glands, leading to xerostomia and a lack of tears.

• Primary Sjögren Syndrome can occur as an isolated disorder, while the secondary form is more often associated with other autoimmune diseases such as RA and SLE.

• Women between the ages of 35 and 45 are more susceptible to Sjögren Syndrome, which is caused by an autoimmune T cell reaction against unknown self-antigens expressed in the gland.

• Amyloidosis is a disorder characterized by the extracellular deposits of misfolded proteins that aggregate to form insoluble fibrils.

• Amyloid deposits cause tissue injury and impair normal function by causing pressure on cells and tissues, but they do not evoke an inflammatory response.

• Amyloid may be systemic or localized, and there are over 20 types of amyloid proteins, including AL, AA, and Amyloid-beta.

• AL protein is produced by plasma cells and is associated with monoclonal plasma cell proliferations.

• AA fibril is the most common form of systemic amyloidosis worldwide and occurs in chronic inflammatory disease and neoplasms.

• Amyloid-beta deposits between neurons in the brain and is involved in Alzheimer's disease, being the main component of the amyloid plaques found in patients.