Immunological monitoring of the inflammatory process: Which variables? When to assess?

Monitoring the immune responses in critically ill patients helps us to understand pathophysiological aspects of inflammation, immune deficiency, and infection, and to assess objective measures of therapeutic success. Monitoring should be adapted to the individual therapeutic approach. We recommend the measurement of substances in plasma that indicate systemic inflammatory processes, such as tumour necrosis factor (TNF), interleukin (IL)-6, and C-reactive protein (CRP), and invasive infection or endotoxaemia, such as procalcitonin (PCT). Moreover, it is important to evaluate the functional activity of the immune system, which can fail like other organs in the process of multiple organ failure. The resulting immunodeficiency results in failure to eliminate invading pathogens. Plasma concentration of IL-10 and of monocytic function and phenotype (HLA-DR+, CD14+ monocytes, ex vivo TNF secretion capacity) are the most valuable measurements for this purpose.