Bone marrow and tissue expression of gpIIb/IIIa, LFA-1, Mac-1 and gp 150,95 glycoproteins

Monoclonal antibodies (MAbs) against platelet glycoproteins gpIIb/IIIa and the leucocyte adhesion molecules LFA-1, Mac-1, and gp 150,95 α chain (CD11a,b,c) and β chain (CD18) have been tested in normal and leukaemic bone marrow, in different human tissues, and in a patient with leucocyte adhesion deficiency (LAD). The effect of these Mabs on platelet aggregation was also tested. GpIIb/IIIa showed widespread distribution, while reactivity of CD11/18 antibodies was limited to haematopoietic cells. Platelets and megakaryocytes were reactive with one CD11a (25.5.2), and with no CD11b/c or CD18 MAbs. GpIIb/IIIa was present on the platelets of the patient with LAD, whereas 25.5.2, (CD11a) bound to his platelets but not to his leucocytes. These data indicate that LFA-1, Mac-1, and gp150,95 are not present on human platelets, but they suggest the existence of crossreacting epitopes on gpIIb/IIIa, which is consistent with the hypothesis that these molecules belong to a supergene family of adhesion molecules.