The abnormal expression of peripheral blood CD4+ T lymphocyte subsets are correlated with primary Sjögren's syndrome complicated with haematological involvement.

Objectives: Complicated primary Sjögren's syndrome (pSS) with haematological involvement (HI) is not uncommon; however, the aetiology of this condition remains obscure. The clinical characteristics, cytokine levels, and expression of peripheral blood lymphocyte subsets (CD4+ T lymphocyte subsets in particular) of patients with pSS-HI were investigated in this study.

Methods: The pSS-HI group (n = 43), the pSS complicated without HI (pSS-non-HI) group (n = 94), and the healthy controls (HCs) group (n = 40) were enrolled in the Second Hospital of Shanxi Medical University. The clinical data were gathered, and cytokines and peripheral blood lymphocyte subsets were quantified using flow cytometry and the Cytometric Bead Array (CBA), respectively.

Results: Patients with pSS-HI were more likely than those without pSS-HI to develop skin involvement, had a higher positive rate of anti-SSA antibody, and had elevated levels of IgA, IgG, and ESR. Compared to the pSS-non-HI group, the number of all lymphocyte subsets was lower in the pSS-HI group. However, the proportion of Th2 cells in the pSS-HI group was higher than those in the pSS-non-HI group. In contrast to the pSS-non-HI group, the pSS-HI group exhibited elevated levels of IL-10 and decreased levels of IL-4. A significant correlation was observed between IL-10 and the number of total T cells, CD4+ T cells, CD8+ T cells, NK cells, Th1 cells, Th2 cells, and Th17 cells. In the context of pSS-HI, protective factors may include the number of Treg cells and CD4+ T cells, whereas risk factors may include IgA and the number of Th2 cells.

Conclusions: An immunological mechanism potentially implicated in the development of pSS-HI may be the elevation of IL-10 and the reduction of peripheral blood CD4+ T cell subsets (particularly Treg cells) and serum IL-4 levels.