FN1 and systemic lupus erythematosus: To evaluate whether β1 or β2 integrin-mediated adhesion were modulated by purified IgG, we evaluated neutrophil adhesion to their respective ligands, fibronectin (via β1 integrins) and fibrinogen (αMβ2 integrin) in the presence of individual SLE- (n = 5), RA- (n = 7) or HC-IgG (n = 6) samples.