chapter 4 immunology - Phagocytosis and opsonization

What is phagocytosis?

Engulfment and internalization of material such as microbes for clearance and destruction.

Which cells are professional phagocytes?

Neutrophils, monocytes, macrophages, and dendritic cells.

What structure forms when a phagocyte engulfs a pathogen?

A phagosome.

What cellular extensions help engulf material during phagocytosis?

Pseudopodia.

What does a phagosome fuse with?

A low-pH lysosome or granule.

What is formed when a phagosome fuses with a lysosome?

A phagolysosome.

What mechanisms destroy pathogens inside phagocytes?

Enzymes, antimicrobial proteins, ROS, and RNS.

What is the first step of phagocytosis?

Recognition of a pathogen by receptors on the phagocyte.

What happens after a pathogen is engulfed by a phagocyte?

It is contained within a phagosome.

What happens after the phagosome forms?

It fuses with a lysosome.

What happens after phagosome-lysosome fusion?

The pathogen is killed and digested.

What is an opsonin?

A molecule that enhances phagocytosis.

What is opsonization?

Coating a pathogen or damaged cell to facilitate recognition and destruction by phagocytes.

What are examples of opsonins listed in the chapter?

MBL, CRP, antibodies, and complement.

Why does opsonization increase phagocytosis?

Phagocytes have receptors that bind the opsonins coating the target.

What do Fcγ receptors on phagocytes recognize?

IgG antibodies bound to antigen.

What do Fcα receptors on phagocytes recognize?

IgA antibodies bound to antigen.

What do complement receptors on phagocytes recognize?

Complement components and fragments.

What are scavenger receptors considered?

A subclass of membrane-bound PRRs.

What can scavenger receptors recognize?

PAMPs, DAMPs, and some non-modified self molecules.

What functions are associated with scavenger receptors?

Phagocytosis, antigen presentation, and clearance of apoptotic cells.