Macrophages express multiple types of receptors on their surface that stimulate phagocytosis of microbes, leading to pathogen internalization and destruction. Many of these receptors, such as Dectin-1, rely on direct recognition of a PAMP on the pathogen surface. However, some receptors that stimulate phagocytosis rely on soluble factors (not associated with the phagocyte membrane) to identify and mark the pathogen for uptake by the phagocyte. That would include which of the following?
a. The class A scavenger receptor
b. The complement receptor
c. The mannose receptor
d. The macrophage C-type lectin receptor
e. The lipid receptor