4.1.1.e Phagocytes

What are antigens?

Proteins or glycoproteins that are intrinsic to the plasma membrane, specific to an organism, which act as markers on cells.

What are opsonins?

Type of antibody that are not very specific and is used to enhance the ability of phagocytes to bind and engulf the pathogen

What are neutrophils?

The most common phagocytes that engulf and digest pathogens

Where are neutrophils manufactured?

Bone marrow

What is the structure of a neutrophil?

- Has a mutilobed nucleus

- Contain a large number of lysosomes

Describe the process of phagocytosis

1. Neutrophil binds to opsonin attached to the antigen of the pathogen

2. The pathogen is engulfed by endocytosis forming a phagosome

3. Lysosomes fuse to the phagosome and release lytic enzymes into it

4. After digestion, the harmless products can be absorbed into the cell

What do macrophages travel in the blood as?

monocytes

Where are macrophages matured?

lymph nodes

What is the role of macrophages?

- Initiates specific responses to invading pathogens

- When macrophage engulfs a pathogen, it does not fully digest it

- The antigen from the surface of the pathogen is saved and moved to a special protein complex on the surface of the cell to become an antigen-presenting cell (APC)

- This exposes the antigen on its surface so the T and B lymphocytes can recognise the antigen

- As there may only be one T cell and one B cell with the correct recognition site for the antigen, the APCs increase the chances that the antigen will come in contact with them.