RESUMO
Spinal cord injury (SCI) is a progressive and complex neurological disorder accompanied by multiple systemic challenges. Peripheral immune dysfunction is a major event occurring after SCI, especially in its chronic phase. Previous works have demonstrated significant changes in different circulating immune compartments, including in T cells. However, the precise characterization of these cells remains to be fully unraveled, particularly when considering important variants such as the time since the initial injury. In the present work, we aimed to study the level of circulating regulatory T cells (Tregs) in SCI patients depending on the duration of evolution. For this purpose, we studied and characterized peripheral Tregs from 105 patients with chronic SCI using flow cytometry, with patients classified into three major groups depending on the time since initial injury: short period chronic (SCI-SP, <5 years since initial injury); early chronic (SCI-ECP, from 5-15 years post-injury) and late chronic SCI (SCI-LCP, more than 15 years post-injury. Our results show that both the SCI-ECP and SCI-LCP groups appeared to present increased proportions of CD4+ CD25+/low Foxp3+ Tregs in comparison to healthy subjects, whereas a decreased number of these cells expressing CCR5 was observed in SCI-SP, SCI-ECP, and SCI-LCP patients. Furthermore, an increased number of CD4+ CD25+/high/low Foxp3 with negative expression of CD45RA and CCR7 was observed in SCI-LCP patients when compared to the SCI-ECP group. Taken together, these results deepen our understanding of the immune dysfunction reported in chronic SCI patients and how the time since initial injury may drive this dysregulation.
RESUMO
Spinal cord injury (SCI) is a disabling neurological condition coursing with serious multisystem affections and morbidities. Changes in immune cell compartments have been consistently reported in previous works, representing a critical point of study for understanding the pathophysiology and progression of SCI from acute to chronic stages. Some relevant variations in circulating T cells have been noticed in patients with chronic SCI, although the number, distribution, and function of these populations remain to be fully elucidated. Likewise, the characterization of specific T cell subpopulations and their related cytokine production can aid in understanding the immunopathological role of T cells in SCI progression. In this sense, the objective of the present study was to analyze and quantify the total number of different cytokine-producers T cells in the serum of patients with chronic SCI (n = 105) in comparison to healthy controls (n = 38) by polychromatic flow cytometry. Having this goal, we studied CD4 and CD8 lymphocytes as well as naïve, effector, and effector/central memory subpopulations. SCI patients were classified according to the duration of the lesion in chronic SCI with a short period of evolution (SCI-SP) (comprised between 1 and 5 years since initial injury), early chronic phase (SCI-ECP) (between 5 and 15 years since initial injury) and late-chronic phase (SCI-LCP) (>15 years since initial injury). Our results show that patients with chronic SCI exhibited an altered immune profile of cytokine-producer T cells, including CD4/CD8 naïve, effector, and memory subpopulations in comparison to HC. In particular, IL-10 and IL-9 production seems to be importantly altered, especially in patients with SCI-LCP, whereas changes in IL-17, TNF-α, and IFN-γ T cell populations have also been reported in this and other chronic SCI groups. In conclusion, our study demonstrates an altered profile of cytokine-producer T cells in patients with chronic SCI, with marked changes throughout the course of the disease. In more detail, we have observed significant variations in cytokine production by circulating naive, effector, and effector/central memory CD4 and CD8 T cells. Future studies should be directed to explore the possible clinical consequences of these changes or develop additional translational approaches in these groups of patients.
