Chapter 31 Infections in the Compromised Host Flashcards
What are the primary factors that affect innate immune system, compromising the host?
complement deficiencies, phagocyte cell deficiencies
What are the secondary factors that affect innate immune systems, compromising the host?
burns, trauma, major surgery, catheterization, foreign bodies (e.g. shunts, prostheses), obstruction
What are the primary factors affecting the adaptive immune system?
T-cell defects, B-cell deficiencies, severe combined immunodeficiency
What are the secondary factors affecting the adaptive immune system?
malnutrition, infectious diseases, neoplasia, irradiation, chemotherapy, splenectomy
What causes primary immunodeficiency?
inherited or occurs by exposure in utero to environmental factors or by other unknown mechanisms. It is rare, and varies in severity depending upon the type of defect.
What causes secondary or acquired immunodeficiency?
underlying disease state or as a result of treatment for a disease
What is one of the best know examples of a primary defect of innate immunity?
chronic granulomatous disease, an inherited failure to synthesize cytochrome b-245, which leads to failure to produce ROS during phagocytosis. As a result, neutrophils cannot kill invading pathogens
What congenital defects are primary defects of innate immunity?
congenital defects in the synthesis of early components in generating classical C3 convertase, particularly C4 and C2
What type of defense system do burns, traumatic injury and major surgery disrupt, and how?
Disrupt the body’s mechanical barriers: Destroy the continuity of skin and may leave poorly vascularized tissue near the body surface, providing a relatively defenseless site for pathogens to colonize and invade.
What is the result of a defect in the stromal microenvironment in which lymphocytes differentiate?
failure to produce B cells (Bruton-type agammaglobulinemia) or T cells (DiGeorge syndrome)
Name and describe the most common form of congenital antibody deficiency?
common variable immunodeficiency; characterized by recurrent pyogenic infections and probably heterogeneous mechanism. Number of immature B cells in marrow tend to be normal, but the peripheral B cells are either low in number or in some cases absent. Where present, they are unable to differentiate into plasma cells in some cases or to secrete antibodies in others.
What is transient hypogammaglobulinemia of infancy?
Occurs naturally in human infants as the maternal serum IgG concentration decays. Serious problem in very premature babies as, depending on gestational age, maternal IgG may not have crossed the placental barrier. characterized by recurrent respiratory infections, associated with low serum IgG concentration, often normalizes abruptly by 3-4 years of age
What is the most common and important cause of acquired immunodeficiency, and what results from it?
malnutrition. The major form, protein-energy malnutrition (PEM) presents as a wide range of disorders, with kwashiorkor and marasmus at the two poles. Results in:
What are the results of the most common and important cause of acquired immunodeficiency?
protein-energy malnutrition results in:
- drastic effects on structure of lymphoid organs
- gross reductions the synthesis of complement components
- sluggish chemotactic responses of phagocytes
- lowered concentrations of secretory and mucosal IgA
- reduced affinity of IgG
- serious deficit in circulating T cell numbers-> inadequate cell-mediated responses
What are the histological features of the thymus in children with protein-energy malnutrition?
acute involution, lobular atrophy, loss of distinction between cortex and medulla, depletion of lymphocytes and enlarged Hassall’s corpuscles
How do lymphocyte counts compare between healthy and malnourished patients?
T cells are decreased in malnourished patients compared to healthy controls. B-cell counts are usually unaltered, and lymphocytes lacking T- and B-cell markers are increased.
What are three examples of treatments causing immunosuppression?
- Cytotoxic agents such as cyclophosphamide and azathioprine cause leukopenia or deranged T- and B-cell function.
- Corticosteroids reduce the number of circulating lymphocytes, monocytes and eosinophils and suppress leukocyte accumulation at sites of inflammation.
- Radiotherapy adversely affects the proliferation of lymphoid cells.