In vitro hyporesponsiveness of CD4+ and CD8+ T cells in septic patients with faecal peritonitis (HUM8P.326)

Abstract The immunological processes behind sepsis are ill defined. Predicting or diagnosing sepsis, based on cellular immune parameters is a research priority. This study quantified differences in peripheral blood mononuclear cell (PBMC) and cytokine levels between septic patients with fecal peritonitis, matched surgical patients (no sepsis) and healthy controls. To assess function, PBMC were stimulated in vitro with anti-CD3±anti-CD28 antibodies. Four days later T and B cell proliferation were measured by CFSE and activation by expression of CD25 and CD69 on T cells and CD86 on B cells. Viability was assessed by flow cytometry. Concentrations of a range of cytokines were determined from plasma and supernatants (post-stimulation) by multiplex cytometric bead array. On day of phlebotomy there were reduced CD4+ and increased CD19+ cells in septic patients. Plasma IL-6 and IL-8 levels were higher in septic patients, IFN-γ and IL-13 were lower. There was reduced proliferation and activation of T cells from septic patients in response to anti-CD3+anti-CD28. Supernatant levels of IFN-γ, TNF-α and interleukins 1β, 5, 6, 13 and 17A were lower in septic patient samples. There were no initial differences in PBMC viability, but septic patient PBMC had reduced survival on incubation. In summary, we found reduced T cell numbers and a functional impairment of remaining T cells in septic patients.To our knowledge this is the first report of an immune function assay across these three groups.