Which surface markers are absent in leukocyte adhesion deficiency type 1?

Leukocyte adhesion deficiency type 1 (LAD-I) is a genetic disorder that affects the immune system, specifically the adhesion and migration of leukocytes (white blood cells) to sites of infection or injury. In this condition, there is a deficiency in the expression of certain surface markers that are critical for leukocyte adhesion.

The surface marker that is absent in leukocyte adhesion deficiency type 1 is CD18. CD18 is a component of the integrins known as beta-2 integrins, which include LFA-1 (CD11a/CD18), Mac-1 (CD11b/CD18), and others. These integrins are essential for leukocytes to adhere to endothelial cells and migrate from the bloodstream into tissues, especially during inflammatory responses. Without CD18, leukocytes cannot properly adhere or migrate, leading to the clinical manifestations of LAD-I, such as recurrent infections and impaired wound healing.

Other options, such as CD19, CD56, and CD4, are not specifically related to the adhesion deficiency in LAD-I. CD19 is a B-cell marker important for B-cell development and signaling. CD56 is a neural cell adhesion molecule that is typically associated with natural killer (NK) cells, and CD4 is a