A male infant has delayed separation of the umbilical cord beyond 3 weeks and repeated bacterial infections of skin and mucosa. Despite large numbers of circulating neutrophils (leukocytosis of 60,000 per microliter), the infected sites show no pus, and there is no neutrophil accumulation in inflamed tissues. Flow cytometry shows absence of CD11b and CD18 on leukocytes. The deficient molecule belongs to which family?
- A Selectins
- B Beta 2 integrins ✓
- C Immunoglobulin superfamily adhesion receptors such as ICAM
- D Fc gamma receptors
Correct answer: B. Beta 2 integrins
Explanation
Leukocyte adhesion deficiency type 1 results from mutations in ITGB2 encoding CD18, the beta chain shared by the beta 2 integrins LFA 1 (CD11a/CD18), Mac 1 (CD11b/CD18), and p150,95 (CD11c/CD18). Neutrophils cannot adhere firmly to endothelium through ICAM 1 or migrate into tissues, so infections occur without pus, wound healing is poor, and umbilical cord separation is delayed with persistent neutrophilia. Selectin defects cause LAD type 2, a separate disorder marked by Bombay blood group phenotype.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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