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Invariant NKT cells found in peripheral blood, not salivary glands, of patients with pSS
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Investigators of a recently published study found invariant natural killer T cells ex vivo in peripheral blood from patients with primary Sjögren’s syndrome, but not in their salivary glands, and detected anti-SSA-specific B cells in target tissue.
The study included 20 patients with primary Sjögren’s syndrome (pSS) who met the American-European Consensus Group criteria with positive antinuclear antibodies, anti-SSA/Ro antibodies and anti-SSB/La antibodies. Nonspecific chronic sialadenitis with various degrees of mononuclear cell infiltration was identified in 16 patients enrolled as a control group. Other autoimmune diseases and hepatitis C were excluded.
All participants underwent the Schirmer test, unstimulated sialometry and minor salivary gland biopsy for histological diagnosis, and peripheral blood was obtained at enrollment.
Significantly higher mean percentages of invariant natural killer (iNKT) cells were detected in the peripheral blood of patients with pSS, however the difference was not significant following in vitro stimulation with alpha-Gal/Cer. The control group had higher mean expansion indices of iNKT cells compared to patients with pSS, with a three-fold increase of V-alpha24 gene expression. Patients with pSS had increased percentages of interleukin-17 (IL-17)+ or interferon-gamma+ iNKT following in vitro activation with alpha Gal/Cer. However, these were not detected in salivary gland mononuclear cells stimulated with alpha-Gal/Cer by flow cytometry or immunofluorescence in either group.
Further analysis of salivary gland mononuclear cells revealed the presence of anti-SSA antigen-specific CD19+ in patients with pSS, but not in the control participants.
“The absences of iNKT in the salivary glands of pSS patients among infiltrating cells [could] contribute to the lack of regulation of autoreactive B cells,” the researchers wrote.
Salivary gland-derived B cells were used to evaluate the production of anti-SSA antibodies.
“Interestingly, we found a statistically significant reduction of anti-SSA auto-Ab when B cells from patients were co-cultured with iNKT cells from patients, but not when the cells were obtained from [controls],” the authors wrote. “The number of iNKT in the cultures was directly related with the inhibitory function displayed by these cells on autoreactive B cells.” – by Shirley Pulawski
Disclosure s : The study was supported by a grant from the Ministero della Università e della Ricerca Scientifica of Italy. The researchers report no other relevant financial disclosures.
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