Case study: Leukocyte adhesion deficiency

Leukocyte adhesion deficiency (LAD) involves issues in neutrophil/monocyte extravasation.

Nitroblue tetrazolium test
The NBT test determines whether NADPH oxidase is functional. LAD patients would have a positive NBT test, indicating that neutrophils are functional in terms of phagocytosis and killing.

Rebuck test
Monitors mobilization of immune cells to region of damaged skin.

Normally, the first cover slip would contain many neutrophils since they are the first recruited cells to arrive. Monocytes appear at around 4 hours. By 8 hours, the slip would be mostly monocytes.

LAD patients would not accumulate leukocytes at all (negative Rebuck test).

LAD 1
Defect in CD18, a subunit of the integrins LFA-1 and MAC-1.

Non-functional LFA-1 and MAC-1 → no arrest and adhesion of neutrophil/monocyte → no movement into tissues.

Phenotypes range depending on % CD18 expression.

Prompt and aggressive antibiotic treatment is the main form of treatment. HST is the only curative function.

LAD 2
Defect in s-Lex → defect in leukocyte rolling.

Still possible for neutrophils/monocytes to adhere and transmigrate.

Antibiotic treatment is an option.

LAD 3
Defective integrin activation and binding.

HST required.