What defect is associated with leukocyte adhesion deficiency (LAD) type 1?

Leukocyte adhesion deficiency (LAD) type 1 is primarily associated with defects in the common β chain of CD18, which is critical for the function of integrins. Integrins are cell surface proteins that facilitate the adhesion of leukocytes (white blood cells) to endothelial cells, allowing them to migrate to sites of infection or injury. In LAD type 1, the mutation in the CD18 subunit disrupts the formation and function of β2 integrins, which leads to impaired leukocyte adhesion, resulting in recurrent infections and a failure to effectively recruit immune cells to sites of inflammation.

The correct answer focuses on this crucial defect that underlies the impaired immune response in LAD type 1, distinguishing it from other conditions or defects that may affect leukocyte function but do not specifically pertain to the β chain in CD18. Such a clear understanding is important in recognizing the pathology and implications of this immunodeficiency.