What is the pathophysiology behind leukocyte adhesion deficiency?

Leukocyte adhesion deficiency (LAD) is primarily associated with a defect in the adhesion of leukocytes to the endothelium, which is crucial for their migration to sites of infection or inflammation. This dysfunction is caused by mutations in genes that code for integrins, particularly the beta-2 integrin (CD18), which are essential for leukocytes to adhere to blood vessel walls and migrate into tissues. Without proper adhesion, leukocytes cannot effectively reach sites of infection, leading to an impaired immune response, recurrent infections, and poor wound healing.

This condition emphasizes the importance of the chemotactic process where leukocytes are directed to the sites of inflammation or infection, and a lack of adhesion means that even if leukocytes are present in circulation, they cannot exit the bloodstream efficiently to perform their functions.

In contrast, the other options relate to different aspects of the immune system. A defect in immunoglobulin production pertains to antibody deficiencies, deficiencies of T cells involve adaptive immune function and do not specifically address the direct problem of leukocyte movement, and deficiencies in complement activation involve the innate immune pathway that enhances opsonization and lysis of pathogens rather than the adhesion of leukocytes. Thus, the defect in chemotaxis due to the inability of