Pathological Mechanisms in Sjögren's Disease Likely Involve the ADP-Ribosyl Cyclase Family Members: CD38 and CD157

Peripheral blood serves both as a source of effector immune cells that migrate to exocrine glands and as a reflection of the immunological changes occurring in patients with Sjögren's disease (SjD). These changes may be linked to the clinical state of these patients. We analyzed total cell counts in the peripheral blood, as well as frequencies of individual leukocyte subpopulations, membrane expression levels of CD38 and CD157, and serum concentrations of soluble sCD38 and sCD157 in SjD patients (n = 40) and age-matched healthy controls (n = 20). Hierarchical clustering based on the cell count of leukocyte subpopulations was employed to identify distinct patient subgroups. Associations between these clusters and clinical parameters were subsequently evaluated. Key findings included a reduction in lymphocyte counts and their subpopulations, alongside increased CD38 expression on CD38⁺ B cells (p = 0.047) and, unexpectedly, on monocytes (p = 0.014) when comparing patients and controls. The involvement of innate immunity was further supported by the differential expression of CD157 across patient samples. Patients with low cell counts exhibited reduced CD157 expression on monocytes and granulocytes (p < 0.02), tested positive for anti-Ro antibodies, and reported severe fatigue. Our findings suggest that innate immune cells, such as monocytes and granulocytes in peripheral blood, are also likely to contribute to the manifestation and progression of SjD. The differential expression of CD157 may reflect distinct immunopathological states and warrants further investigation, as its precise role in exocrine gland involvement and extra-glandular manifestations lies beyond the scope of this study.