24 Questions
What is the most likely underlying condition in this infant?
Leukocyte adhesion deficiency
What is the significance of the positive nitroblue tetrazolium dye reduction test?
It confirms the diagnosis of chronic granulomatous disease
What is the likely cause of the infant's omphalitis?
Impaired migration of leukocytes to the site of infection
What is the classification of the genetic defect in leukocyte adhesion deficiency?
Autosomal recessive
What is the role of CD18 (LFA-1) in leukocyte function?
Adhesion to endothelial cells
Which of the following is NOT a feature of leukocyte adhesion deficiency?
Elevated immunoglobulin E levels
What is the likely consequence of a defect in superoxide production?
Impaired killing of bacterial pathogens
Which of the following is a complication of leukocyte adhesion deficiency?
Omphalitis
What is the function of C5a in the complement system?
Neutrophil chemotaxis and histamine release from mast cells
What is the function of LFA-1 (CD11a/CD18) in neutrophils?
Tight adhesion
What is the result of a defect in the LYST gene?
Chediak-Higashi Syndrome
Which cytokine is secreted by Th1 cells and activates macrophages to increase the inflammatory response?
IFN-γ
What is the result of a defect in CD18?
Leukocyte adhesion deficiency type 1
What is the function of PECAM-1 (CD31) in neutrophils?
Transmigration
What is the function of C3b in the complement system?
Opsonization
What is the result of a defect in the LFA-1 (CD18) adhesion molecule?
Leukocyte adhesion deficiency type 1
What is the function of CD14 in the recognition of LPS?
Co-receptor for TLR4
What is the result of a granuloma?
Chronic inflammation
What is the primary function of Toll-Like Receptors (TLRs)?
To recognize and respond to pathogens and damaged cells
What is the result of Leukocyte Adhesion Deficiency?
Impaired neutrophil migration
Which of the following is NOT a component of the acute inflammatory response?
Granulomas
What is the role of Hageman Factor XII in the inflammatory response?
Activation of bradykinin
What is the primary characteristic of chronic inflammatory response?
Formation of granulomas
What is the result of Chediak-Higashi Syndrome?
Defective lysosomal function
Study Notes
Physical Examination
- Tenderness and erythema at the umbilical stump with serosanguinous drainage
- Umbilical cord remains attached from birth
- Induration along the surrounding tissues
- Bulging right tympanic membrane with opacification and loss of light reflex
Laboratory Evaluation
- Hemoglobin: 16.5 g/dL
- Leukocyte count: 45,500/mm3
- Platelet count: 185,000/mm3
- C-reactive protein: Elevated
- Nitroblue tetrazolium dye reduction test: Positive
Inflammatory Response
- Toll-Like Receptors (TLRs) recognize PAMPs and DAMPs, triggering an inflammatory response
- Arachidonic acid: lipooxygenase pathway à leukotrienes à ↑ neutrophil chemotaxis
- Bradykinin, Hageman Factor XII: ↑ vasodilation, vascular permeability, and pain sensitivity
- Inflammatory cytokines: IL-1, TNF-⍺, IL-6 à acute inflammatory process
- Damaged endothelial cells: ↑ nitric oxide à ↑ vasodilation
Neutrophil Migration
- Margination: ↑ vascular permeability à hemoconcentration à ↑ neutrophil contact with endothelium
- Rolling: Neutrophil: Sialyl LewisX; Endothelium: E-selectin, P-selectin
- Tight Adhesion: Neutrophil: LFA-1 (CD11a/CD18), Mac1 (CD11b/CD18); Endothelium: ICAM-1 (CD54)
- Transmigration: Neutrophil: PECAM-1 (CD31); Endothelium: PECAM-1 (CD31); driven by chemotaxis (LTB4, IL-8, C5a)
Disorders of Leukocyte Migration
- Leukocyte Adhesion Deficiency (LAD): absence of LFA-1 (CD18) à impaired tight adhesion
- Chediak-Higashi Syndrome: impaired microtubule polymerization à ↓ neutrophil chemotaxis; LYST gene defect
Chronic Inflammation
- Fibrosis and angiogenesis
- Granulomas: maintained by IL-12 and TNF-⍺; composed of multinucleated giant cells, fibroblasts, lymphocytes, and epithelioid cells
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