Mucin inhibition of lymphocyte function does not require specific mucin-ligand interactions

Mucins are large highly glycosylated molecules that have been postulated to interfere with certain cell-cell interactions. Steric, charge and specific signalling effects have been postulated for the inhibition by cell-surface mucin molecules. In this report we evaluate the inhibitory effects of bovi ne submaxillary mucin (BSM), a mucin without specific lymphocyte interactio ns, on lymphocyte function. BSM inhibits the adhesion of lymphocytes when c oimmobilized with intercellular adhesion molecule-1 (ICAM-1) and blocks the activation of T lymphocytes when coimmobilized with anti-CD3. These data d emonstrate a general mucin effect on lymphocyte adhesion and activation tha t is primarily steric in nature and implicates mucins as general barriers t o lymphocyte-tumour cell interactions. Mucin blockade of cell-cell interact ions may explain why mucinous tumours are often associated with a poor prog nosis.