The immune response of the human brain to abdominal surgery
In patients, inflammatory molecules such as TNF‐α and interleukins appear in CSF within 12 hours after major surgery.4 Although such clinical observations are in line with a series of experimental studies,2 the time course pattern beyond the immediate postsurgery phase of immune activation within the human CNS is unknown, and how the systemic pro‐ and anti‐inflammatory response16 is associated with cognitive performance is largely unexplored.
The use of positron emission tomography (PET) and radioligands selective for the translocator protein (TSPO) provide an opportunity for translational studies exploring brain immune activity after surgery. In brain parenchyma, TSPO is primarily expressed in microglia and to a lesser extent in astrocytes. This protein can be viewed as a marker for CNS immune activation, because changes in TSPO levels have been shown to reflect changes in glial cell activity.19 TSPO expression is typically elevated in several acute and chronic CNS disorders involving the immune system21 as well as in animal models of acute inflammation26 or stroke.19 With regard to periphery‐to‐brain interactions, lipopolysaccharide (LPS)‐induced acute systemic inflammation is followed by a rapid and transient activation of the brain immune system, as demonstrated using the TSPO radioligand [11C]PBR28 in nonhuman primates27 and humans.28
Here, we examined the impact of major surgery on the human brain immune system by a longitudinal series of PET examinations of TSPO binding in otherwise healthy patients undergoing abdominal surgery and how changes in glial cell activation relate to systemic inflammatory response and cognitive performance.