Influence of delayed sample processing on blood immune cell phenotypes, immune cell responses and serum anti-influenza vaccine antibody titres.

Provision of blood from distant research partners to a central laboratory can result in delayed blood processing prior to assessment of immune parameters. It is important to evaluate the effect of such delays on immune parameters. This study investigated the effect of storage of blood at room temperature for up to 72 h prior to processing and analysis on a range of immune parameters. Blood was collected from 10 healthy participants and analysed immediately (day 0) or after storage at room temperature for 24, 48 or 72 h (days 1, 2 and 3). A full blood count, immune cell phenotypes (flow cytometry), plasma cytokines, chemokines and soluble receptors (multiplex immunoassay), neutrophil and monocyte phagocytosis (flow cytometry), whole blood cytokine responses to stimulation and antibody titres to the seasonal influenza vaccine were assessed. The full blood count, most immune cell phenotypes, monocyte phagocytosis and anti-influenza vaccine antibody titres were little affected by blood storage of ≤72 h prior to processing. Plasma cytokine concentrations increased with blood storage time while whole blood responses to stimulation with lipopolysaccharide or phytohaemagglutinin decreased with blood storage time. In conclusion, while fresh blood is optimal for analysing human immune parameters, it is possible to store blood for up to 72 h at room temperature and obtain reliable measures of several immune markers. However, plasma cytokines and related mediators as well as whole blood cultures should be analysed using freshly isolated blood. Storage of blood for longer than one day may result in the unreliable assessment of these outcomes.