Elevated proportion of TLR2- and TLR4-expressing Th17-like cells and activated memory B cells was associated with clinical activity of cerebral cavernous malformations

Abstract

Background

Recent evidences have suggested the involvement of toll-like receptor (TLR)-4 in the pathogenesis of cerebral cavernous malformations (CCM). Elevated frequency of TLR⁺T-cells has been associated with neurological inflammatory disorders. As T-cells and B-cells are found in CCM lesions, the objective of the present study was to evaluate the cytokine profile of T-cells expressing TLR2 and TLR4, as well as B-cell subsets, in asymptomatic (CCM_Asympt) and symptomatic (CCM_Sympt) patients.

Methods

For our study, the cytokine profile from TLR2⁺ and TLR4⁺ T-cell and B-cell subsets in CCM_Asympt and CCM_Sympt patients was investigated using flow cytometry and ELISA. T-cells were stimulated in vitro with anti-CD3/anti-CD28 beads or TLR2 (Pam3C) and TLR4 (LPS) ligands.

Results

CCM_Symptc patients presented a higher frequency of TLR4⁺(CD4⁺ and CD8⁺) T-cells and greater density of TLR4 expression on these cells. With regard to the cytokine profile, the percentage of TLR2⁺ and TLR4⁺ Th17 cells was higher in CCM_Sympt patients. In addition, an elevated proportion of TLR4⁺ Tc-1 cells, as well as Tc-17 and Th17.1 cells expressing TLR2 and TLR4, was observed in the symptomatic patients. By contrast, the percentage of TLR4⁺ IL-10⁺CD4⁺ T cells was higher in the CCM_Asympt group. Both Pam3C and LPS were more able to elevate the frequency of IL-6⁺CD4⁺T cells and Th17.1 cells in CCM_Sympt cell cultures. Furthermore, in comparison with asymptomatic patients, purified T-cells from the CCM_Sympt group released higher levels of Th17-related cytokines in response to Pam3C and, mainly, LPS, as well as after activation via TCR/CD28. Concerning the B-cell subsets, a higher frequency of memory and memory activated B-cells was observed in CCM_Sympt patients.

Conclusions

Our findings reveal an increase in circulating Th17/Tc-17 cell subsets expressing functional TLR2 and, mainly, TLR4 molecules, associated with an increase in memory B-cell subsets in CCM patients with clinical activity of the disease.