Radiation induces iatrogenic immunosuppression by indirectly affecting hematopoiesis in bone marrow

The immune system plays a vital role in cancer therapy, especially with the advent of immunotherapy. Radiation therapy induces iatrogenic immunosuppression referred to as radiation-induced lymphopenia (RIL). RIL correlates with significant decreases in the overall survival of cancer patients. Although the etiology and severity of lymphopenia are known, the mechanism(s) of RIL are largely unknown. We found that irradiation not only had direct effects on circulating lymphocytes but also had indirect effects on the spleen, thymus, and bone marrow. We found that irradiated cells traffic to the bone marrow and bring about the reduction of hematopoietic stem cells (HSC) and progenitor cells. Using mass cytometry analysis (CyTOF) of the bone marrow, we found reduced expression of CD11a, which is required for T cell proliferation and maturation. RNA Sequencing and gene set enrichment analysis of the bone marrow cells following irradiation showed down-regulation of genes involved in hematopoiesis. Identification of CD11a and hematopoietic genes involved in iatrogenic immune suppression can help identify mechanisms of RIL

Detection of Central Retinal Artery Occlusion by Point-of-Care Ultrasound in the Emergency Department: A Case Series.

Central retinal artery occlusion (CRAO) is a rare, but serious, diagnosis that can lead to blindness, most often due to thromboembolic disease. In the emergency department (ED), CRAO can present as acute, painless loss of vision. Physicians need quick ways to rule in this diagnosis due to the time-sensitive nature of the event. We describe two patients in this cases series who present to the same ED with unilateral painless vision loss and histories that include notable risk factors such as thromboembolic and atherosclerotic disease. Upon arrival, point-of-care ultrasound (POCUS) done at the bedside allowed for quick determination of CRAO. The importance of this case series is to emphasize the efficacy of POCUS in evaluating patients with painless vision loss in the ED setting