Analysis of Mucosal- Associated Invariant T Cell Levels And Their Correlation With Tumor Immune Status In Patients With Brain Tumors

Introduction: Primary brain tumors refer to a heterogeneous group of tumors arising from cells within the CNS, and can be benign or malignant. In recent years, experimental evidence suggests that, despite the presence of blood-brain barrier (BBB) and lack of discrete lymphoid tissue, there are immunocompetent cells (TILs-Tumor infiltrating lymphocytes) within the brain parenchyma. Many of these cells are T-Lymphocytes known as CD8+ Mucosal-associated invariant T (MAIT) cells, which proliferate with stimulation, and are cytotoxic to tumor cells in vitro. To evaluate the frequency of unconventional MAIT cells in the setting of brain tumors by expression analysis of their three defining markers CD3D, KLRB1 (CD161) and a TCR a-chain variant Va7.2 (TRAV1-2 gene). Methodology: The study involved collecting EDTA blood samples and fresh brain tissue biopsies from selected population followed by RNA extraction and cDNA synthesis for measurement of relative expression analysis in blood and tissues samples. Expression data was generated by semi-quantitative real time PCR. Results: The outcome of this study demonstrated higher expression level of  CD3D, KLRB1 (CD161) and a TCR a-chain variant Va7.2 (TRAV1-2 gene) in the blood of patients compared to the tissue samples showed little to no transmigration of these MAIT cells in the diseased tissues. Also, the expression of genes under-investigation was observed decreasing in both blood and tissue samples with the progression of tumor. Conclusion: MAIT cells might undergo depletion in the tumor micro-environment due to chronic activation induced exhaustion of these cells.