Fig. 8

Integrative scheme of the potential mechanisms involved in the phagocytosis of wasteosomes obtained from post-mortem extracted CSF by THP-1 macrophages.The absence of FAIM3 in THP-1 macrophages and the absence of IgM opsonizing the CSF wasteosomes (binding to their NEs) indicate that the phagocytosis by THP-1 macrophages does not occur through the IgM-FAIM3 interaction. However, phagocytosis could occur through CD206 and CD35 receptors, which are both present in THP-1 macrophages. In the first case, the CD206 receptor can interact with mannose or other carbohydrates located in the wasteosomes. In the second one, the CD35 receptor can recognize the C3b that opsonizes wasteosomes once they arrive at the CSF. The opsonization with C3b in the CSF can be produced through the lectin pathway (L), triggered by the binding of MBL with the wasteosomes, and through the alternative pathway (A), triggered by the contact between C3 and wasteosomes, but not through the complement pathway (C), because IgM do not opsonize wasteosomes in the CSF. Note that wasteosomes are obtained from post-mortem extracted CSF and are altered wasteosomes that may show waste elements. At the central nervous system interfaces, in which waste elements are enclosed into the polyglucosan structure, the wasteosomes are not opsonized by MBL or C3b, and they interact with CD206 + macrophages but not with CD35 + or FAIM3 + macrophages. See text for details