Module 4: Non-specific immune response

Question 1

Describe the primary defences against pathogens in animals

Answer 1

Skin - a physical barrier to pathogens
Mucous membranes - Protect body openings by producing mucus to trap pathogens
Blood clotting - Plug wounds to prevent pathogen entry and blood loss
Expulsive reflexes - For example sneezing and coughing. Both attempt to expel foreign objects.

Question 2

Describe the process of phagocytosis

Answer 2

Cells at the site of a wound release cytokines to attract to phagocytes.
Phagocyte recognises the antigens on pathogen.
An opsonin may be attached to the antigen to aid phagocytosis.
The phagocyte engulfs the pathogen.
The pathogen is contained in a phagosome.
A lysosome fuses with the phagosome to become phagolysosome.
Enzymes break down the pathogen.
Digested pathogen absorbed by phagocyte.
Antigens combine with MHC in cytoplasm.
The phagocyte presents the antigen to activate other cells in the immune system.
It is known as an antigen presenting cell (APC).

Question 3

Name four types of cell you may see in a blood smear. For each one describe how you would be able to recognise it.

Answer 3

Red blood cell - No nucleus
Monocyte (type of phagocyte) - Biggest white blood cell, large, kidney bean shaped nucleus, non grainy cytoplasm.
Neutrophil (type of phagocyte) - Multi lobed nucleus, grainy cytoplasm.
Lymphocyte - Much smaller than phagocytes, nucleus takes up most of cell, little cytoplasm can be seen but it is not grainy.