TREM2 and Alzheimer disease: Herein we have shown that in AD sTREM2 concentration was increased concomitantly with a decrease of TREM2-expressing monocytes, a reduction of TREM2 level of receptor expression and Aβ42-phagocytosis by such monocytes Taken together these results suggest that in vitro Aβ42-phagocytosis is impaired in AD as a consequence of the ligation of monocytes-expressed TREM2 by the increased amounts of its soluble, decoy form.