CELLS REGULATE THE ACTIVITIES OF CYTOKINES BY GLYCOSYLATION

Cytokines, including the interferons, interleukins, colony stimulating factors, and chemokines, are first-line, hormone-like defense molecules that orchestrate immune functions in a nonspecific, i.e., antigen-independent, way. The multiplicity of cytokines has a genetic basis, but oligomerization and especially glycosylation add to the heterogeneity and signaling functions of the cytokines. It is theorized that the cell uses glycosylation of cytokines to alter its functions. This is achieved by changing the specific biological activities, by altering diffusability, tissue distribution, and pharmacokinetics, and by targeting different populations of responsive cells. One interesting possibility is that multiple glycosylation forms compete for receptor binding resulting in a natural selection process or possibly antagonistic effects. Cytokines as ligands often are multimers and cytokine receptors are almost without exception heterodimers, which within receptor families share common subunits. Hence, carbohydrate-lectin interactions might contribute to ligand dimerization and receptor recognition through multivalent bindings.