BetaB1-crystallin: identification of a candidate ciliary body uveitis antigen.

PURPOSE: Perineuclear anti-neutrophil cytoplasmic antibody (pANCA), a marker antibody present in 12% of patients with anterior uveitis, recognizes cytoplasmic antigens in the nonpigmented ciliary body epithelium, a probable site of immunologic reactivity in this inflammatory disease. In this study, a recombinantly isolated pANCA monoclonal antibody was used to identify the corresponding antigenic target(s) in the ciliary body.

METHODS: Proteins from microdissected eye bank ocular ciliary body tissue were used to identify the corresponding ANCA antigen. Parallel two-dimensional protein gels were used for simultaneous identification of candidate antigenic protein spots by Western blot analysis and as a source of material for proteomic analysis. Multiple independent methods including Western blot analysis, confocal microscopy, and RT-PCR were used to provide additional characterization of the candidate protein.

RESULTS: Proteomic analysis suggested that beta B1 (betaB1)-crystallin is the primary ciliary body antigen. The presence of betaB1-crystallin in the human ciliary body was confirmed by Western blot with a betaB1 specific anti-peptide antibody. Confocal microscopy revealed colocalization of the antigenic reactivity of both anti-betaB1 antibody and monoclonal pANCA. RT-PCR confirmed the presence of betaB1-crystallin RNA in the ciliary body tissues.

CONCLUSIONS: This study identified betaB1-crystallin as a new cytoplasmic ciliary body antigenic target of a marker autoantibody associated with uveitis. This characterization of betaB1-crystallin outside the lens raises questions about its extralenticular expression, intracellular role, and potential target of inflammation in uveitis.