Anti-retinal immune response in sarcoid uveitis: A potential role for PCLO as an antigenic target

To explore the autoimmune component of sarcoid uveitis (SU) by analyzing serum anti-retinal antibodies (ARAs), identifying targeted retinal proteins, T- and B-cell receptor repertoires and HLA genotype.

Material from 45 sarcoidosis patients with no presenting uveitis (SNPU) and 46 with SU was analyzed. Serum ARAs and targeted retinal layers were assessed using indirect immunofluorescence staining. HuScan analysis identified autoantibody-targeted linear epitopes. Validation included a bead-based assay for anti-Piccolo Presynaptic Cytomatrix Protein (PCLO) antibodies and an ELISpot assay for PCLO-reactive T-lymphocytes. T cell receptor beta (TCRB) and B cell receptor heavy (BCRH) repertoire analyses were performed using next-generation sequencing and HLA class II genotypes were determined by sequence-specific primer analysis.

ARAs were more prevalent in SU patients than in SNPU patients (52 vs. 22 %, p = 0.003), with significant more reactivity against the nuclear retinal layer (32 vs. 7 %, p = 0.005). HuScan identified autoantibodies against three retinal proteins, including PCLO. Bead-based analysis showed higher anti-PCLO autoantibody levels in ARA-positive patients (median: 913.3 vs. 544.5, p = 0.035), and PCLO-directed T-lymphocytes were present in ARA-positive SU patients. Two TCRB clusters were identified in four unique ARA positive patients, while absent in ARA negative patients. No HLA allele association with ARA status could be detected.

Our findings reveal an association between serum ARA-positivity and SU, suggesting a link to autoimmune processes. An humoral and cellular response against the retinal protein PCLO was identified, highlighting PCLO as a potential autoimmune target in ARA-positive patients. Additionally, specific TCRB clusters were found to correlate with ARA status.