Lymphocytes induce resorption of cartilage by producing catabolin

Mononuclear cells from pig blood, when cultured in the presence of lectins (concanavalin A or phytohaemagglutinin), release a factor that induces resorption of proteoglycan in explants of live bovine nasal cartilage. The factor had mol.wt. 20000 and pI 4.6-5.0, and was indistinguishable from the cartilage-catabolic protein catabolin isolated from culture medium of explants of pig synovial tissue. Since much of the catabolin from the mononuclear cells arose from the non-adherent population (98% lymphocytes) it was concluded that lymphocytes (and possibly monocytes) make catabolin.