Systemic immune responses in patients with spine surgery related infections

Surgical site infections (SSIs) are significant complications that can occur after spine surgery. Compared with systemic infections such as sepsis, or localised musculoskeletal infections such as periprosthetic joint infection, the immune responses in postoperative infection of the spine are poorly understood. A deeper understanding may provide clinically relevant diagnostic or therapeutic options.

This study examined changes in immune cell profiles in the blood of patients who developed infections after spinal surgery (Infection group, I, n = 17) compared to control patients without infections (Non-infection, NI, n = 20). The two groups were matched by age, body mass index (BMI), and the invasiveness of the surgical procedure. Peripheral blood mononuclear cells (PBMCs) were collected after surgery and subjected to high-dimensional mass cytometry.

Cluster analysis identified 46 immune cell clusters, 30 of which exhibited significant differences between the I and NI patients. Natural killer cells as well as myeloid dendritic cells were decreased in I patients compared to NI patients (p=0.0269; and p=0.0267, respectively). Conversely, Th17, CD69⁺ and HLA-DR⁺ CD4⁺ T cells were significantly increased in I patients compared to NI patients (p=0.0422, p=0.0267; p=0.0267, respectively). ROC curve analysis of immune cell counts demonstrated potential for differentiating NI from I patients.

This study reveals that patients with SSI exhibit a significantly altered immune cell profile, with greatest differences observed in increased HLA-DR⁺ CD4⁺ T cells and decreased numbers of several innate immune cells. The diagnostic potential of these markers may prove clinically relevant, and further research into the impact of activation and exhaustion may yield future therapeutic strategies.