TLR-2 and TLR-4 agonists favor expansion of CD4+ T cell subsets implicated in the severity of neuromyelitis optica spectrum disorders

Abstract

Background: High frequency of circulating Th17 cell subsets expressing TLR2, TLR4 and TLR9 was observed in Neuromyelitis optica spectrum disorder (NMOSD) patients, a severe humoral autoimmune disease of the central nervous system. Our objective was to evaluate the direct effects of different TLR ligands on CD4⁺ T-cells form those patients.

Methods: CD4⁺ T-cell cultures from NMOSD and healthy individuals were stimulated with different TLR ligands and the cell proliferation and cytokine profile was analyzed by [³H] TdR up take and ELISA/ cytometry, respectively. The plasma levels of CD14 were determined by ELISA.

Results: Here, Pam3C (TLR2) and LPS (TLR4) induced significant cell proliferation and IL-6, IL-17 and IL-21 production by CD4⁺ T-cells from NMOSD. Additionally, while both TLR ligands were more potent in favoring the expansion of T_FH-like cells, Pam3C reduced the frequency of IL-10-secreting FoxP3⁺and FoxP3^- CD4⁺ T-cells. With regard to disease severity, the levels of IL-6, IL-17 and IL-21 produced by CD4⁺ T-cells, as well as the frequency of T_FH-like cells, in response to TLR2 and TLR4 agonists were positively correlated with neurological disabilities and the occurrence of new acute relapses during follow up. Finally, circulating levels of CD14, an indirect marker of microbial translocation, were positively correlated with IL-6, IL-17 and IL-21 release by Pam3C- and LPS-activated CD4⁺ T-cells.

Conclusions: In summary, our data suggest that microbial antigens may affect NMOSD outcomes by favoring an imbalance between Th17 and TFH-like cells and regulatory T cell subsets.

Keywords: CD14; CD4(+) T cells; Cytokines; NMOSD; TLR ligands.