Quantification of IgM molecular response by droplet digital PCR as a potential tool for the early diagnosis of sepsis

Abstract

Evaluation of host immune response to infection at the molecular level is a promising avenue to obtain diagnostic and prognostic tools for the clinical management of patients with sepsis. A recent report from Cajander and colleagues [1] has shown the potential of HLA-DR mRNA quantification by real-time PCR as a biomarker of immunosuppression in these patients. IgM is the first immunoglobulin produced in response to infection. In a pilot study, we have employed a next generation quantitative PCR method (nanoliter-sized droplet technology paired with digital PCR (ddPCR)) for detecting the early transcriptomic response of IgM in blood from patients with sepsis. Approval for the study protocol for both scientific and ethical aspects was obtained from the Committee for Clinical Research of Hospital Clínico Universitario, Valladolid, Spain. Written informed consent was obtained directly from each patient or a legal surrogate. The target gene transcript was IGHM, which encodes the constant region of the mu heavy chain, which defines the IgM isotype [2]. In blood, the cells producing IgM transcripts are B lymphocytes expressing CD20 [3], which was employed as housekeeping gene.