Phagocytes

What are phagocytes involved in

The non-specific immune response (phagocytosis)

What are the types of phagocytes

Neutrophils and macrophages

Where are phagocytes made and stored

They’re produced continuously in the bone marrow and stored there before being distributed into the blood

What do neutrophils look like

They are lobed and have a grainy appearance

How do neutrophils carry out phagocytosis

• chemicals released by pathogens and body (eg histamine) attract neutrophils to site - chemotaxis

• Neutrophils move towards pathogen

• Receptor proteins on surface of neutrophil attach to antigen on surface of pathogens

• Cell surface membrane of neutrophil extends out and around pathogen engulfing it and trapping pathogen within phagocytic vacuole - endocytosis

• Neutrophil secretes digestive enzymes onto vacuole - phagosome fuses with lysosome to form phagolysosome

• After digestion, neutrophils die (pus)

How do macrophages differ to neutrophils

They’re larger, more long-lived and move into organs from the bone marrow (eg lungs, liver, spleen, kidney and lymph nodes)

What happens once macrophages leave the bone marrow

They travel in the blood as monocytes then develop into macrophages once they have left the blood

How do macrophages initiate a specific immune response

• they carry out phagocytosis, but do not completely destroy the pathogens

• They cut the pathogens so they can display the antigens of the pathogen on their surface

• They use MHCs and form antigen presenting cells (APCs)

• These displayed antigens can then be recognised by lymphocytes