Normal expression of the adhesive structure Mo-1 on monocytes from patients with Glanzmann's thrombasthenia

The glycoprotein complex GPIIb-IIIa of the platelet membrane and CD18 of the monocyte membrane have been established as being the central figure for the adhesion processes of the corresponding cells. The molecular structure of these 2 GPs bears some similarities. It was proposed recently that LFA-1 and Mo-1 (CD18 family) and GPIIb-IIIa might be encoded by the same gene. For this purpose, we studied the expression of Mo-1, Mo-2 (as control) receptors on monocytes and GPIIIa and GPIIb-IIIa on platelets of two GT patients as compared to normal healthy subjects. Monoclonal antibodies anti Mo-1, MO-2, AP-3 and AP-2 were used to measure the expression of the respective antigens by indirect immunofluorescence procedure. The fluorescence of the labelled cells was analysed with an Ortho Cytofluorograph 50-H. The resulting Mean Fluorescence Intensity (MFI) values of AP-2 and AP-3 showed that the patients had a total absence of GPIIb-IIIa antigens. However, Mo-1, as well as those of control Mo-2, in patients (MO-1: 672 and 716; Mo-2: 453 and 637) were similar to that of normal subjects (Mo-1: 735 +/- 74; Mo-2: 585 +/- 35; mean +/- SEM). Therefore, the normal expression of Mo-1 receptors on the monocytes of Glanzmann's thrombasthenia patients suggests different genomic regulations for Mo-1 antigens on the monocyte and GPIIb-IIIa complex on the platelet.