T and B cell clonal expansion in Ras associated lymphoproliferative disease (RALD) as revealed by next generation sequencing

Ras associated lymphoproliferative disease (RALD) is an autoimmune lymphoproliferative syndrome (ALPS)-like disease caused by mutations in KRAS or NRAS. The immunological phenotype and pathogenesis of RALD have yet to be extensively studied. Here we report a thorough immunological investigation of a RALD patient with a somatic KRAS mutation. Patient lymphocytes were analyzed for phenotype, immunoglobulin levels and T cell proliferation capacity. T and B cell receptor excision circles (TREC and KREC, respectively), markers of naive T and B cell production, were serially measured over three years. T and B cell receptor repertoires were studied using both traditional assays as well as next generation sequencing (NGS). TREC and KREC dramatically declined with time, as did T cell receptor diversity. NGS analysis demonstrated T and B clonal expansions and marked restriction of T and B cell receptor repertoires compared to healthy controls. Our results demonstrate, at least for our reported RALD patient, how peripheral T and B clonal expansions reciprocally limit lymphocyte production and restrict the lymphocyte receptor repertoire in this disease. Decreased naive lymphocyte production correlated with a clinical deterioration in our patient's immune status, suggesting TREC and KREC may be used as an aid in monitoring disease progression. Both the methodologies used here and the conclusions regarding immune homeostasis may be applicable to the research of ALPS and other immune dysregulation syndromes. This article is protected by copyright. All rights reserved.