Immune tumoral microenvironment in gliomas: focus on CD3+ T cells, Vδ1+ T cells, and microglia/macrophages.

Abstract

Gliomas are histologically defined as low-grade gliomas (LGG) and high-grade gliomas (HGG). The most common type of HGG is the glioblastoma (GBM). We aimed to determine the immunological characteristics of CD3 T-cells, Vδ1 T-cells, and microglia/macrophages infiltrating brain gliomas. We collected 24 formalin-fixed paraffin-embedded samples issued from 19 cases of GBM and 5 cases of LGG. An immunohistochemical analysis was performed using anti-CD3, anti-Vδ1, and anti-iba-1 antibodies. Labelling indexes (LI) of CD3 and Vδ1 were evaluated quantitatively, and other CD3, Vδ1, and iba-1 staining characteristics were evaluated qualitatively. The median age of patients was 49years in GBM and 52years in LGG. The sex ratio was 1.4 and GBM predominated in males (p = 0.05). In GBM, the medians of CD3-LI and Vδ1-LI were 30 and 3.5 respectively. CD3-LI inversely correlated with survival in GBM cases (r = - 0.543; p = 0.016). CD3 staining intensity correlated with CD3-LI (p < 0.0001) and with the survival in GBM cases (p = 0.003). Compared to LGG, the CD3-LI, the intensity of intra-tumoral Vδ1 staining, and the amount of iba-1 were higher in GBM (p = 0.042; p = 0.014; and p = 0.001 respectively). The iba-1 organization was more amoeboid in older patients and more branched in younger patients (p = 0.028) and tended to be more amoeboid in cases with high iba-1 amount (p = 0.09). Our results suggest that a high level of CD3-LI and a strong intra-tumoral infiltration of Vδ1 T-cells as well as a high involvement of TAM can be considered potential markers of poor prognosis of GBM. However, this requires further studies on more balanced GBM-LGG sample, including an expanded panel of biomarkers.