Genetic Inhibition of Nfatc2 Attenuates Asparaginase Hypersensitivity in Mice

The development of a T cell‐dependent antibody response to asparaginase (ASNase) is the most common adverse effect of treatment with this chemotherapeutic agent for pediatric acute lymphoblastic leukemia (ALL). Anti‐ASNase antibodies decreases ASNase levels and drug efficacy and can mediate anaphylaxis. Transcription factors of the nuclear factor of activated T cells (NFAT) family play a critical role in Th cell activation, differentiation, and effector function. Here we show that a member of this family, Nfatc2 (NFAT1), upregulates Th2 responses, with Nfatc2 ‐deficient ASNase‐immunized mice being completely protected from anaphylaxis. Consistent with this, our clinical data demonstrate increased risk of ASNase hypersensitivity in pediatric ALL patients who express the NFATC2 rs6021191 intronic variant, which increases Nfatc2 expression, whereas the risk of ASNase hypersensitivity is decreased in ALL Down syndrome patients, who overexpress NFAT pathway inhibitors. Hypothesis Nfatc2 deficiency protects mice against ASNase‐induced hypersensitivity by suppressing type 2 immunity. Methods Nfatc2 ‐deficient mice and WT littermates were immunized with native E. coli ASNase using aluminum hydroxide adjuvant, after which immune cell phenotype and levels of basophil activation, cytokines, and ASNase‐specific antibody were determined. Hypersensitivity reactions to ASNase were assessed by detecting hypothermia with rectal thermometry. β‐hexosaminidase release was used for in vitro analysis of the degranulation of peritoneal mast cells (PMCs) obtained from naïve and ASNase‐immunized mice, while passive cutaneous anaphylaxis, passive systemic anaphylaxis, and active systemic anaphylaxis models were used for in vivo determinations. Results Nfatc2 ‐deficient mice were protected against ASNase hypersensitivity reactions. Naïve Nfatc2 ‐deficient mice had fewer CD4 + IL‐4 + cells and lower IL‐4 and IL‐13 levels than wild‐type mice. ASNase‐immunized Nfatc2 ‐deficient mice had increased levels of Treg cells and the regulatory cytokines, IL‐10 and TGF‐β 1 , along with decreased plasma IgG and IgE anti‐ASNase and total IgE levels. Consistent with this, basophils/peritoneal mast cells from Nfatc2 ‐deficient mice had decreased FcɛRI expression and IgE‐mediated activation. Conclusion Nfatc2 deficiency decreases ASNase hypersensitivity by increasing regulatory responses and attenuating type 2 immune responses to ASNase immunization. Nfatc2 may be a promising target for the prevention of ASNase‐induced hypersensitivity. Support or Funding Information University of Pittsburgh School of Pharmacy & NIH Grants RO1 CA216815