Although immune signaling has emerged as a defining feature of the glioma microenvironment, how the underlying structure of the glioma-infiltrating T-cell population differs from that of the blood from which it originates has been difficult to measure directly in patients. High-throughput sequencing of T-cell receptor (TCR) repertoires (TCRseq) provides a population-wide statistical description of how T cells respond to disease. We have defined immunophenotypes of whole repertoires based on TCRseq of the α-and β-chains from glioma tissue, nonneoplastic brain tissue, and peripheral blood from patients. Using information theory, we partitioned the diversity of these TCR repertoires into that from the distribution of VJ cassette combinations and diversity due to VJ-independent factors, such as selection due to antigen binding. Tumor-infiltrating lymphocytes (TILs) possessed higher VJ-independent diversity than nonneoplastic tissue, stratifying patients according to tumor grade. We found that the VJ-independent components of tumor-associated repertoires diverge more from their corresponding peripheral repertoires than T-cell populations in nonneoplastic brain tissue, particularly for low-grade gliomas. Finally, we identified a "signature" set of TCRs whose use in peripheral blood is associated with patients exhibiting low TIL divergence and is depleted in patients with highly divergent TIL repertoires. This signature is detectable in peripheral blood, and therefore accessible noninvasively. We anticipate that these immunophenotypes will be foundational to monitoring and predicting response to antiglioma vaccines and immunotherapy.T-cell receptor | immunoprofiling | glioma | glioblastoma | immunooncology T he potential for immunotherapy to alleviate progression and recurrence in glioma has inspired intense study of the immunological phenotypes underlying the regulation and selection of tissue-infiltrating lymphocytes (TILs). Motivated by the prospect of targeted therapy, previous studies of glioma have undertaken large-scale genomic and gene expression analysis. These studies revealed distinct phenotypic states or subtypes that stratify gliomas and resemble different glial lineages (1-3). Although immunological gene expression classifications have been associated with clinical outcomes and prognosis (4, 5), precision immunotherapy will ultimately rely on manipulation of the T-cell population that infiltrates gliomas and its underlying repertoire of T-cell receptors (TCRs). However, the structure and intertumoral heterogeneity of the TIL population in gliomas has not been described. Here, we use whole repertoire sequencing of TCRs from glioma tissue and matched peripheral blood to discover novel immunological phenotypes with implications for noninvasive patient monitoring.Local antitumor potential is, in part, a function of the TCR repertoire expressed by T cells that surveil the CNS beyond the bloodbrain barrier. Through somatic V(D)J recombination including random nucleotide insertion in each T-cell, the α-and β-cha...