Successful use of anti-PD-1 antibody to treat multiple metastatic carcinomas in a patient with xeroderma pigmentosum: case report and literature reviewMai Itoyama1, Akihiro Ohara1, Kazuki Yokoyama1, Shun Yamamoto1, Ken Kato1, Taisuke Mori2, Hiroshi Igaki3, Eiji Nakano4,5, Naoya Yamazaki4, Kuniko Sunami6, Chikako Nishigori5,7, Yoshitaka Honma11. Department of Head and Neck, Esophageal Medical Oncology, National Cancer Center Hospital2. Department of Diagnostic Pathology, National Cancer Center Hospital3. Department of Radiation Oncology, National Cancer Center Hospital4. Department of Dermatologic Oncology, National Cancer Center Hospital5. Department of Dermatology, Kobe University Graduate School of Medicine6. Department of Laboratory Medicine, National Cancer Center Hospital7. Hyogo Blood Center, Japanese Red CrossContact (Mai Itoyama):Adress: 5-1-1 Tsukiji, Chuo-ku, Tokyo, JapanEmail: [email protected]

BACKGROUND: Although basophils are considered to play an important role for maintenance of type 2 inflammation in atopic dermatitis (AD), studies on basophils in AD patients are limited. Some studies have reported the activation status, including CD203c and CD63, of peripheral blood basophils in AD patients. OBJECTIVE: To examine the features of circulating basophils in AD patients by assessing and comparing cell surface marker expressions, total serum IgE, and basophil responsiveness to stimulation between AD patients and healthy controls (HCs). In addition, to examine the correlations among AD severity, laboratory factors, and features of basophils. METHODS: Blood samples from 38 AD patients and 21 HCs were analyzed. Basophil response markers CD203c and CD63, and expression of surface-bound IgE and FcεRI on basophils were measured. CD203c and CD63 expressions induced by stimulation with anti-IgE and anti-FcεRI antibodies were measured. Clinical/laboratory factors including total serum IgE were examined for correlations with these basophil parameters. RESULTS: Basophils in AD patients were activated spontaneously without stimulation and exhibited low responsiveness to anti-IgE antibody stimulation. Responsiveness to anti-FcεRI stimulation was higher than anti-IgE stimulation, contrary to HCs. FcεRI expression on basophils was higher in AD patients than in HCs, although surface-bound IgE on basophils was equivalent. Total serum IgE had negative correlations with surface-bound IgE and CD63 responsiveness to anti-IgE stimulation. CONCLUSIONS: Our findings illustrate the characteristic basophil status in AD. Despite high serum IgE and high basophil FcεRI expression, surface-bound IgE on basophils remained relatively low and basophils were spontaneously activated under steady-state conditions.