Leukocyte-adhesion deficiency 2 is due to the absence of __________.
Leukocyte  adhesion  deficiencies  (LADs)  stem  from  inherited defects in adhesion molecules that impair leukocyte recruitment to sites of infection, resulting in recurrent bacterial infections.

LAD1 is caused by defects in the β 2  chain that is shared by the integrins LFA-1 and Mac-1. 
LAD2 is caused by a defect in a fucosyl transferase that is required to synthesize functional sialyl-Lewis X, the ligand for E- and P-selectins.

​Reference-Robbins BASIC PATHOLOGY 10th edition pg-172
Selectin
LFA-1
MAC 1
Sialyl-Lewis X