Leukocyte adhesion deficiency: molecular basis and functional consequences.

Leukocyte adhesion deficiency disease is characterized by a mutation in the gene encoding the beta-subunit shared by three adhesive heterodimers, LFA-1, Mac-1 (CR3) and p150,95 expressed by leukocytes. An absent or abnormal beta-subunit leads to defective expression of the three heterodimers. Severe and moderate phenotypes of the disease are defined by absent and low surface expression of the adhesion molecules. The disease causes an inability of phagocytic cells to adhere to endothelial cells and thereafter to migrate to sites of infections. Severe widespread life-threatening bacterial and fungal infections are the consequences of this abnormality. Cure of the disease can be effected by allogeneic bone marrow transplantation. T-lymphocyte adhesion to various cells is also impaired; its consequences are, however, limited because of the existence of other T-cell-adhesive pathways. Nevertheless, haploidentical bone marrow graft rejection does not occur in the severe phenotype, an indication for possible immunotherapy with LFA-1 specific monoclonal antibodies.