Recombinant human type II collagen (rhCII) was produced using both the HT1080 mammalian cell expression system (rhCIIht) and a baculovirus expression system (rhCIIbac). The biosynthesis of CII requires extensive post-translational modifications, such as the hydroxylation of prolyl and lysyl residues and glycosylation of hydroxylysyl residues. Amino acid analyses indicated that the rhCIIbac was adequately hydroxylated at prolyl residues but underhydroxylated at lysyl residues and underglycosylated compared with tissue-derived hCII, while rhCIIht was hyperhydroxylated and hyperglycosylated at lysyl residues. When the murine collagen-induced arthritis (CIA) model was used to investigate the immunological properties of the two forms of recombinant CII, each induced a high incidence of arthritis following immunization of susceptible mice when emulsified with complete Freund s adjuvant (CFA). However, the severity of the arthritis, as assessed by the number of affected limbs, was significantly higher in mice immunized with rhCIIht than in mice immunized with rhCIIbac. These data indicate that the degree of hydroxylysine glycosylation may play a role in the induction of the arthritogenic response to CII. Each of the recombinant collagens was comparable to tissue-derived hCII in their ability to induce tolerance and suppress arthritis when given as intravenous or oral tolerogens. Taken together, our data suggest that recombinant CII can be prepared in adequate amounts for therapeutic uses and that the material is immunologically comparable to tissue-derived hCII when used to induce tolerance.