Exploration of the combined role of immune checkpoints and immune cells in the diagnosis and treatment of ankylosing spondylitis: a preliminary study immune checkpoints in ankylosing spondylitis

Objective:
Immune checkpoints have emerged as promising therapeutic targets for autoimmune diseases. However, their specific roles in the pathophysiology of ankylosing spondylitis (AS) remain poorly understood.

Methods:
Hip ligament samples were collected from two patient groups: (1) those with AS and femoral head deformity and (2) those with femoral head necrosis but without AS, undergoing hip arthroplasty. Label-Free Quantification (LFQ) Protein Park Analysis was used to profile the protein composition of the ligaments. To validate the expression of key proteins, peripheral blood samples from 104 AS patients, obtained from a public database, were analyzed. Pathway exploration was conducted using KEGG, GO, and GSVA to identify mechanisms regulated by immune checkpoints in AS progression. Cell infiltration levels were calculated using xCell, while LASSO regression was employed to Doramapimod select key immune cells. Correlations between immune checkpoints and immune cell populations were analyzed, and drug sensitivity screening was performed to identify potential therapeutic candidates targeting immune checkpoints in AS. Immunohistochemistry (IHC) was used to confirm the expression of key genes.

Results:
HLA-DMB and HLA-DPA1 were found to be downregulated in the ligaments of AS patients, which was further validated using peripheral blood datasets and IHC. Expression differences were notable in several immune cell types, including CD8+ T central memory (Tcm) cells, CD8+ T cells, CD8+ effector memory (Tem) cells, osteoblasts, Th1 cells, and CD8+ naive T cells. In particular, the infiltration levels of CD8+ Tcm and CD8+ naive T cells showed a strong positive correlation with HLA-DMB and HLA-DPA1 expression. LASSO regression analysis identified immune cells with strong predictive value for AS, with area under the curve (AUC) scores of 0.98, 0.81, and 0.75 across three models. Additionally, the study revealed that HLA-DMB and HLA-DPA1 play roles in Th17 cell differentiation, with both Th17 cell differentiation and the NF-kappa B signaling pathway found to be activated in AS patients. Drug sensitivity analysis indicated that AS patients are particularly responsive to therapies such as doramapimod and GSK269962A.

Conclusion:
This study highlights immune checkpoints and immune cells as potential targets for diagnostic and therapeutic strategies in AS.