Th1 Predominance and Perforin Expression in Minor Salivary Glands from Patients with Primary Sjögren's Syndrome

Objectives of this study were to examine the cytokine and perforin mRNA expression in minor salivary glands from patients with primary Sjögren's syndrome (pSS), searching for possible correlation with clinical parameters and to identify the dominant cytokine pattern in the different groups. Oral mucosa biopsy samples from 42 pSS patients were studied. Total RNA was analysed by normalized RT-PCR using oligo-dT as the RT primer and IL-2, IFN-gamma, IL-12, IL-18, IL-4, IL-10, TGF-beta, TNF-alpha and perforin-specific primers for amplification. Results were analysed taking into account: (1) biopsy grade I to IV (Chisholm's classification); (2) diagnosis of either definite pSS (n=30) or probable pSS (n=12), following the European classification criteria (ECC), and (3) length of disease evolution from the beginning of symptoms to the time of biopsy, using an arbitrary cut-off point of 12 months. This studied showed that Th1-related cytokines (IL-2, IFN-gamma, IL-12, IL-18, TNF-alpha) and perforin were present in most samples. IL-4 (Th2) was totally absent but other Th2 and regulatory cytokines (IL-10, TGF-beta) were detected in the majority of samples. No significant differences were found between definite and probable pSS nor between grades II, III, IV and fibrous tissue biopsies. A statistically significant increase of IL-2 (P=0.012) and IFN-gamma (P=0.019) was observed in samples from patients with longer disease evolution, whereas the two Th1-inducer cytokines IL-12 and IL-18 were equally and highly expressed in all samples. In conclusion, a predominant Th1 pattern of cytokines was observed in all pSS samples, irrespective of biopsy classification. In addition, a significant increase of Th1 cytokine expression frequency was associated with longer disease evolution.