25.33 : 免疫不全症

Immunodeficiency diseases occur due to exposure to immunosuppressive agents, poor development of lymphoid organs, or viral infections.

Prolonged use of immunosuppressive drugs often destroys lymphocytes to the extent that even minor infections can turn life-threatening.

Severe Combined Immunodeficiency—SCID—is caused by various embryonic and genetic defects, leading to a significant deficit of B and T cells.

Children with SCID have little to no defense against pathogens. Early interventions like donor hematopoietic stem cells or gene therapies to correct the affected genes in the patient's HSC can substantially enhance survival rates.

Acquired Immune Deficiency Syndrome—AIDS—is caused by the human immunodeficiency virus. HIV transmission typically occurs through blood-contaminated needles, unsafe sexual intercourse, or transmission from an infected mother to her fetus.

HIV infects CD4 cells and establishes itself using the viral enzyme reverse transcriptase. It then integrates into the DNA of the host cell, leading to viral replication and the destruction of T cells.