IMMU-12. T CELL SEQUESTRATION IN POSTERIOR FOSSA TUMORS

Abstract INTRODUCTION T cell dysfunction contributes to immune escape in patients with cancer and is particularly severe CNS tumors. sequestration a contributing mechanism of lymphopenia lymphoid organ contraction occurring treatment naive mice Glioblastoma. Our group demonstrated that this phenomenon mediated by loss S1P1 surface expression on T-Cells within the bone marrow. We murine models reversing via stabilization licenses activating therapies. As pediatric brain tumors much more commonly involve posterior fossa brainstem, present work set out assess whether also occurs located cerebellum (medulloblastoma, high grade glioma). METHODS CT2A glioma cells were orthotopically implanted into C57BL/6 mice. Blood, spleen, marrow analyzed when became sizable (Day 18-21). Flow cytometry was utilized measure total, CD4+, CD8+ counts, as well proportion expressing S1P1. RESULTS Compared injected methylcellulose, bearing cerebellar significantly decreased splenic weight, increased CD4, CD8 counts marrow, CONCLUSIONS associated S1P1, previously forebrain, cerebellum, suggesting genesis independent location brain. Future project will add additional tumor histology our analysis measuring effects response therapies these