Is Inhibitor of differentiation 3 involved in human primary Sjögren's syndrome?

OBJECTIVES: Inhibitor of differentiation 3 (Id3)-deficient mice show sicca symptoms, lymphocyte infiltration of exocrine glands and positive anti-Ro/SSA and anti-La/SSB antibodies, all hallmarks of primary Sjögren's syndrome (pSS). The impairment of Id3 in T cells and, possibly, in salivary glandular epithelial cells (SGECs) seems to be involved. This animal model prompted us to investigate the role of Id3 in human pSS.

METHODS: Quantitative Id3 expression in peripheral T cells, cultured SGECs and in total minor salivary glands was assessed by RT-PCR in pSS patients and controls. After Id3 sequencing, we investigated two single nucleotide polymorphisms (SNPs) (c.313G>A and g.-156A>G) in a case-control study of 212 Caucasian pSS patients and 168 controls.

RESULTS: Quantitative Id3 expression was not decreased in pSS patients nor in SGECs, in T cells or in minor salivary glands. As well, patients and controls did not differ in allele and genotype frequencies of Id3 SNPs (P = 0.67 and P = 0.71 for the c.313G>A and the g.-156A>G, respectively). Neither SNP was associated with a pattern of autoantibody secretion.

CONCLUSION: Although the Id3-deficient mouse model represents an attractive model for human pSS, Id3 expression is not impaired in SGECs, peripheral T cells and in labial salivary glands in pSS patients and Id3-relevant SNPs do not give evidence of genetic predisposition in Caucasian pSS patients.