Immune markers of disease severity and treatment response in pediatric acquired aplastic anemia

Background To investigate the immune status among pediatric patients with aplastic anemia (AA) and explore PNH-status, T-regulatory and NK-cell frequency as potential markers of clinical response. Methods Data were retrospectively analyzed from twenty-six patients diagnosed with AA. PNH populations, T- and NK-subsets were determined via flow cytometry. Results At diagnosis, 9/23 patients with severe AA (SAA) versus 1/3 with moderate AA (MAA) were PNHpos. Among PNHpos patients treated with ATG based immunosuppression, 2/6 had a complete response (CR), while 4/6 had a partial response (PR), similarly 2/6 PNHneg patients had a CR and 4/6 had a PR. Lymphocyte subset immunophenotyping revealed that T-regulatory cells represented 7.2% of total lymphocytes at diagnosis. Their frequency varied with disease severity (5.5% for SAA and 14.1% for MAA) and response (8.9% for CR and 1.5% for PR), generally increasing following therapy with IST (14.6%). The NK cell frequency was not substantially different based on disease severity or response. Conclusions Neither PNH cell populations, nor NK cell frequency corresponded with disease severity or response. T-regulatory cell frequency, although not statistically significant given the small sample size, corresponded with both severity and response, indicating potential utility as a prognostic tool. Pediatr Blood Cancer 2013; 60: 455-460. (C) 2012 Wiley Periodicals, Inc.