Relationship between [¹²³I]FP-CIT SPECT data and peripheral CD4 + T cell profile in newly-diagnosed drug-naïve Parkinson’s disease patients

Background: Dysregulation of the CD4 + T cell compartment occurs in Parkinson’s Disease (PD). Nonetheless, the exact relationship with dopamine transporter (DAT) SPECT denervation patterns is currently unknown. Methods: Expression of transcription factors and levels of circulating CD4 + T cell subsets were assessed in peripheral blood mononuclear cells (PBMC) from 23 newly diagnosed drug-naïve PD patients. Semi-quantitative [¹²³I]-FP-CIT SPECT data, i.e. uptake in the most and least affected putamen (maP, laP) and caudate (maC, laC), total striatal binding ratio (tSBR), and total putamen-to-caudate ratio (tP/C) were obtained. Results: FOXP3 mRNA levels correlated with the uptake in maC (r = − 0.542, P = 0.011), laP (r = − 0.467, P = 0.033), and tSBR (r = − 0.483, P = 0.027). Concerning flow cytometry analysis of circulating CD4 + T cell subsets, a significant relationship between tP/C, caudate uptake, and the levels of both T helper (Th)1 and 2, was detected. Furthermore, we found significant correlations between the uptake in maP and the total count of naïve and activated T regulatory cells (Treg) (r = − 0.717, P = 0.001; r = − 0.691, P = 0.002), which were confirmed after the Benjamini–Hochberg correction for multiple comparisons using a false discovery rate at level q = 0.10. Levels of circulating naïve Treg were higher (P = 0.014) in patients with more extensive dopaminergic denervation, suggesting a compensatory phenomenon. Conclusions: Peripheral CD4 + T cell immunity is involved in early-stage PD and novel correlations with striatal DAT loss were observed.