Etiopathogenic Role of Surfactant Protein D in the Clinical and Immunological Expression of Primary Sjogren Syndrome

Objective. To analyze the etiopathogenic role of genetic polymorphisms and serum levels of surfactant protein-D (SP-D) in primary Sjogren syndrome (pSS). Methods. We analyzed 210 consecutive patients with pSS. SFTPD genotyping (M11T polymorphism rs721917) was analyzed by sequence-based typing and serum SP-D by ELISA. Results. Thirty-two patients (15%) had the Thr11/Thr11 genotype, 80 (38%) the Met11/Met11 genotype, and 96 (46%) the Met11/Thr11 genotype; 2 patients could not be genotyped. Patients carrying the Thr11/Thr11 genotype had a higher prevalence of renal involvement (13% vs 1% and 4% in comparison with patients carrying the other genotypes, p = 0.014). Serum SP-D levels were analyzed in 119 patients (mean 733.94 +/- 49.88 ng/ml). No significant association was found between serum SP-D levels and the SP-D genotypes. Higher mean values of serum SP-D were observed in patients with severe scintigraphic involvement (851.10 +/- 685.69 vs 636.07 +/- 315.93 ng/ml, p = 0.038), interstitial pulmonary disease (1053.60 +/- 852.03 vs 700.36 +/- 479.33 ng/ml, p = 0.029), renal involvement (1880.64 +/- 1842.79 vs 716.42 +/- 488.01 ng/ml, p = 0.002), leukopenia (899.83 +/- 661.71 vs 673.13 +/- 465.88 ng/ml, p = 0.038), positive anti-Ro/SS-A (927.26 +/- 731.29 vs 642.75 +/- 377.23 ng/ml, p = 0.006), and positive anti-La/SS-B (933.28 +/- 689.63 vs 650.41 +/- 428.14 ng/ml, p = 0.007), while lower mean values of serum SP-D were observed in patients with bronchiectasis (489.49 vs 788.81 ng/ml, p = 0.019). Conclusion. In pSS, high SP-D levels were found in patients with severe glandular involvement, hypergammaglobulinemia, leukopenia, extraglandular manifestations, and positive anti-Ro/La antibodies. The specific association between SP-D levels and pulmonary and renal involvements may have pathophysiological implications.