Previously, we showed that Mycoplasma pulmonis can agglutinate trypsin-treated but not untreated erythrocytes (RBCs). This suggested that cryptic RBC binding sites were blocked by glycophorin, which is anchored to the RBC cytoskeletal network. In this report we show that RBCs from ankyrin-deficient mice in which the linkage between glycophorin and cytoskeleton is disrupted are agglutinated by M. pulmonis without trypsin treatment. This result demonstrates that diffusion of glycophorin is sufficient to allow recognition of cryptic binding sites by M. pulmonis. It also suggests that diffusion of surface proteins away from the area of close contact may play an important role in M. pulmonis-host cell interactions.