A 2-year-old boy suffers from recurrent bacterial infection of his ears,sinuses,lungs,and skin;laboratory studies indicate absence of sialylated Lewis X on his leukocytes.He is diagnosed with leukocyte adhesion deficiency type 2 (LAD-2).Which type of adhesive interaction required for leukocyte migration is defective in this boy?
A)E-selectin ligand binding to E-selectin
B)CD4 binding to class II MHC
C)VLA-4 binding to VCAM-1
D)Ig Fc receptor binding to Ig-coated cells
E)LFA-1 binding to ICAM-1

Question

Quizplus · Accepted Answer

Leukocyte adhesion deficiency type 2 (LAD-2)is a rare genetic disorder characterized by severely impaired neutrophil rolling and adhesion to activated endothelium.The cause is a defect in the synthesis of sialylated Lewis X,the carbohydrate ligand on neutrophils and other leukocytes that is required for binding to E-selectin and P-selectin on cytokine-activated endothelium.In a clinically similar disorder called LAD-1,there is absent or deficient expression of the CD11CD18 family of integrins (of which LFA-1 is a member).Adhesion interactions mediated by CD4,Fc receptor,and VLA-4 are normal in patients with LAD-2.

A 2-Year-Old Boy Suffers from Recurrent Bacterial Infection of His