Immunosuppression
Basics
Basics
Basics
Description
Description
Congenital or acquired deficiency in the ability to fight infection:- Antibody production (B-cell)
- Cellular immunity (T-cell)
- Phagocytic dysfunction
- Complement deficiency
- Breach of skin/mucosal barriers
Etiology
Etiology
- Congenital disorders
- Immunosuppressive medications
- Aging:
- Immunosenescence
- Poor circulation and wound healing
- Chronic (lung, kidney, or heart) disease
- HIV infection:
- CD4 count determines susceptibility to pathogens
- Diabetes:
- Hyperglycemia impairs immune response
- Vascular insufficiency
- Malnutrition:
- Poverty
- Alcoholism and drug abuse
- Eating disorders
- Asplenia:
- Functional asplenia (sickle cell disease) or surgical splenectomy increases risk of infection with encapsulated organisms
- Organ transplantation:
- Antirejection medications suppress immune response
- Infections may be donor derived, recipient derived, or nosocomial
- Increased risk of viral pathogens, such as cytomegalovirus, Epstein–Barr virus, and human herpes viruses
- Time elapsed since transplantation is crucial, as different patterns of infection arise in early, intermediate, and late posttransplantation periods
- Malignancy
- Chemotherapy:
- Increased risk of infection with pyogenic bacteria and fungi
- Infection risk related to length and severity of neutropenia
- Neutropenia:
- Defined as absolute neutrophil count (ANC) <500/mm3 or <1,000/mm3 with an anticipated nadir of <500/mm3
- In the U.S., gram-positive organisms are the leading etiology of infection
- Gram-negative organisms are somewhat less common but often virulent
- Polymicrobial infections are increasingly frequent
- Anaerobic isolates remain relatively rare
- The risk of fungal pathogens increases with prolonged neutropenia (>1 wk), prior use of broad-spectrum antibiotics, or intense chemotherapy
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