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How does the human immune system respond to exposure to a pathogen? -…
How does the human immune system respond to exposure to a pathogen?
Adaptive Immunity
The adaptive immune response
is specific
has a diverse range of responses
has memory
has self-tolerance
B and T lymphocytes
are capable of recognising foreign molecules, called antigens ('antibody generators'). Antigens are components of bacteria, viruses, fungi, worms, tumor cells and other non-cellular materials.
Humoral
(extracellular pathogens) neutralise pathogens
cell-mediated
(intercellular pathogens) destroy pathogen infected cells.
Innate Immunity
Responsible for non-specifically stopping foreign materials from spreading throughout the body, once they’ve made it through the barriers to infection
Phagocytosis
- The process by which phagocytes engulf and destroy foreign or unwanted material (e.g. pathogens)
Natural killer cells
- They constantly patrol the body, and are important in defence against virus-infected and cancerous cells.
Inflamation
- The accumulation of fluid, plasma proteins and white blood cells that occurs when tissue is damaged or infected. Example: redness, heat, swelling, pain or loss of function in the affected area.
The Compliment System
- A set of more than 30 different proteins which float around in the blood. When the pathogen breaks through the barriers to infection the complement system is activated.
Primary and Secondary Immunity
The primary immune response is triggered when a pathogen enters the body for the first time. There are no existing memory cells so antibody production is slow, and as a result, the individual shows symptoms. The secondary immune response is triggered when a pathogen enters the body for the following time. There are existing memory cells so antibody production is fast, and as a result, the individual shows no symptoms.
T cells
Helper T cells
- Release chemicals that activate the cloning of cytotoxic T cells and B cells and increase macrophage activity after that antigen has been recognised.
Cytotoxic T cells
- Move to the site of infection and release chemicals that destroy infected cells.
Memory T cells
- Remain in the body to respond to future infections by the same antigens.
Suppressor T cells
- Suppress the immune response when the infection has been defeated.
Common Responses to Different Pathogens
Bacteria
- Neutrophilia
Viruses
- Leukopenia
Fungi
- Neutrophilia; monocytosis
Protozoa
- Esinophilia; altered red cell architecture; increased IgM and IgG.
Macroparasites
- Eosinophila increased IgE