Identification, Quantitation, and Purification of a 36 kDa Circulating Protein Associated With Active Pars Planitis

Purpose. To establish a correlation between the presence of a 36 kDa protein in the blood ofpatients with pars planitis and to characterize and purify this protein.Methods. Blood samples were obtained from patients with pars planitis and other types ofuveitis and from various controls. Samples were treated with polyethelene glycol and proteinA and were analyzed on 10% SDS-PAGE for the presence of a 36 kDa protein. Quantitativeestimation of the level of this protein was determined by densitometric tracing of the stainedgels. Polyclonal antibodies were raised by immunizing New Zealand White rabbits with amixture of the gel fragment containing the 36 kDa protein (p-36) and complete Freund'sadjuvant. These antibodies were used in the immunoafnnity purification of this protein.Results. The levels of p-36 were sixfold to eightfold higher in 81% of the patients with activepars planitis than in controls (P < 0.05). Furthermore, the levels of this protein correlatedwith disease activity. A partial amino terminal sequence analysis revealed that p-36 may be anovel protein. It has been purified from the patient's blood using affinity chromatography.Conclusions. A 36 kDa protein (p-36) is found in elevated concentrations in the blood of manypatients with active pars planitis. Its putative role in the etiopathogenesis of pars planitis isunknown. Invest Ophthalmol Vis Sci. 1996;37:1870-1876.A. leading cause of blindness in the United States isuveitis.