Inflammatory reactions: initiation, tissue injury, and impaired defense
THE CONTEXT
Inflammation begins with recognition of microbes or damaged cells by tissue cells. It contributes to tissue injury in several diseases, while inadequate inflammation increases susceptibility to infection.
Initiation of inflammation
•
Macrophages and other tissue cells recognize microbes and damaged cells and release mediators that trigger vascular and cellular inflammatory reactions.
•
Edema is accompanied by an influx of plasma proteins from the blood.
Examples of inflammatory tissue injury
•
Cytokines are involved in the injury associated with septic shock.
•
Lymphocytes and macrophages are involved in rheumatoid arthritis.
•
Eosinophils and IgE antibodies are involved in asthma. Asthma may present as a chronic illness with repeated acute exacerbations.
•
Macrophages and fibroblasts are involved in pulmonary fibrosis.
Inadequate inflammation
•
Inadequate inflammation typically manifests as increased susceptibility to infections.
•
Causes of impaired inflammation include reduced leukocyte production resulting from replacement of bone marrow by cancers such as leukemias, immunosuppressive agents used for graft rejection and autoimmune disorders, and malnutrition.
•
Inherited disorders of leukocyte function are rare but provide information about the mechanisms of leukocyte responses.