Secondary Immunodeficiency Diseases .HIV infection and AIDS.
Secondary (acquired) immunodeficiencies are non-congenital defects of the immune system, resulting from external factors rather than inherited genetic mutations.
Causes (Etiology )
- 1 Infections
HIV (most important globally).
Other chronic infections (e.g., measles, tuberculosis).
- 2 Malnutrition
Protein-calorie malnutrition → lymphoid tissue atrophy.
Vitamin deficiencies (A, C, zinc) → impaired barrier and cellular immunity.
- 3 Immunosuppressive therapy
Corticosteroids → lymphocyte apoptosis, decreased cytokines.
Cytotoxic chemotherapy → bone marrow suppression.
Immunosuppressive drugs (e.g., cyclosporine).
- 4 Malignancies
Leukemias and lymphomas → affect bone marrow and immune organs.
Multiple myeloma → defective antibody production.
- 5 Metabolic diseases
Diabetes mellitus → impaired neutrophil function and poor circulation.
Clinical Features
Increased susceptibility to infections (opportunistic and common pathogens).
Poor wound healing.
Frequent, severe, or atypical infections.
HIV Infection and AIDS
HIV (Human Immunodeficiency Virus) infection is a retroviral infection leading to progressive immune system destruction.
AIDS (Acquired Immunodeficiency Syndrome ) is the most advanced stage of HIV infection, defined by severe CD4+ T cell depletion and opportunistic infections or cancers.
Virology
Retrovirus (Lentivirus family).
Major components:
- Envelope proteins: gp120 (binds CD4), gp41 (fusion).
- Core proteins: p24 antigen (important for diagnosis).
- Enzymes: reverse transcriptase, integrase, protease.