Radiation immunodynamics in patients with glioblastoma receiving chemoradiation.

Introduction: This is a prospective, rigorous inquiry into the systemic immune effects of standard adjuvant chemoradiotherapy, for WHO grade 4, glioblastoma. The purpose is to identify peripheral immunologic effects never yet reported in key immune populations, including myeloid-derived suppressor cells, which are critical to the immune suppressive environment of glioblastoma. We hypothesize that harmful immune-supportive white blood cells, myeloid derived suppressor cells, expand in response to conventionally fractionated radiotherapy with concurrent temozolomide, essentially promoting systemic immunity similar what is seen in chronic diseases like diabetes and heart disease. Methods: 16 patients were enrolled in a single-institution, observational, immune surveillance study where peripheral blood was collected and interrogated by flow cytometry and RNAseq. Tumor tissue from baseline assessment was analyzed with spatial proteomics to link peripheral blood findings to baseline tissue characteristics. Results: We identified an increase in myeloid-derived suppressor cells during the final week of a six-week treatment of chemoradiotherapy in peripheral blood of patients that were not alive at two years after diagnosis compared to those who were living. This was also associated with a decrease in CD8+ T lymphocytes that produced IFNγ, the potent anti-tumor cytokine. Discussion: These data suggest that, as in chronic inflammatory disease, systemic immunity is impaired following delivery of adjuvant chemoradiotherapy. Finally, baseline investigation of myeloid cells within tumor tissue did not differ between survival groups, indicating immune surveillance of peripheral blood during adjuvant therapy may be a critical missing link to educate our understanding of the immune effects of standard of care therapy for glioblastoma.

Neurotrophic factor Neuritin modulates T cell electrical and metabolic state for the balance of tolerance and immunity.

The adaptive T cell response is accompanied by continuous rewiring of the T cell's electric and metabolic state. Ion channels and nutrient transporters integrate bioelectric and biochemical signals from the environment, setting cellular electric and metabolic states. Divergent electric and metabolic states contribute to T cell immunity or tolerance. Here, we report that neuritin (Nrn1) contributes to tolerance development by modulating regulatory and effector T cell function. Nrn1 expression in regulatory T cells promotes its expansion and suppression function, while expression in the T effector cell dampens its inflammatory response. Nrn1 deficiency causes dysregulation of ion channel and nutrient transporter expression in Treg and effector T cells, resulting in divergent metabolic outcomes and impacting autoimmune disease progression and recovery. These findings identify a novel immune function of the neurotrophic factor Nrn1 in regulating the T cell metabolic state in a cell context-dependent manner and modulating the outcome of an immune response.

Systemic depletion of lymphocytes following focal radiation to the brain in a murine model.

Severe radiation-related lymphopenia is common and associated with decreased survival in patients with several solid tumors. As the mechanisms underlying systemic lymphopenia are poorly understood, we developed an animal model to study the effects of brain radiation on lymphocytes and cytokines. C57 BL/6 and BALB/c mice received focal brain irradiation (4 Gy x 10 fractions or 2 Gy x 30 fractions). Weekly total lymphocyte counts (TLC), lymphocyte subsets and cytokines in blood and lymph nodes were measured. Non-irradiated lymph nodes were collected and examined before, during, and after radiation. We found that systemic TLC decreased rapidly irrespective of mouse strain or radiation schedule. 4 Gy x 10 resulted in a 42% and 75% & 70% and 49% TLC reduction in C57 BL/6 and BALB/c mice respectively. 2 Gy x 30 caused a 70% / 49% decrease in TLC in C57 BL/6 and BALB/c. Similar trends were seen for total T cells, CD4+, regulatory T and CD8+ cells. Changes in lymph node architecture and cellular composition correlated with the development of systemic lymphopenia. Three weeks after radiation, TLC returned to 60-80% of baseline, preceded by increased IL-7 levels in the lymph nodes. Focal brain radiation in mice results in significant systemic lymphodepletion.