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What is the immune system? What is it composed of?

The immune system is an organised system which contains organs, cells and molecules that interact together to defend the body against disease (e.g pathogenic microorganisms and cancer).


What is an infectious disease, inflammatory disease and cancer?

Infectious disease: A disorder caused my microbes.
Inflammatory disease: A disorder which results from autoimmunity of the body (immune system attacking body).
Cancer: A rapidly growing set of cells.


What is the lymphatic system in humans? What are the primary and secondary lymphoid organs and how are they organised into these two groups?

The lymphatic system is the organs of the immune system, the organs are arranged as either primary or secondary organs based on function.
Primary: production of white blood cells (lymphocytes), includes thymus and bone marrow,
Secondary: sites where immune responses initiate, includes spleen, tonsils and lymph nodes


What function do the two primary lymphoid organs serve?

These are the thymus and the bone marrow. Both are primary because of their role in producing white blood cells.
Bone marrow: The source of stem cells which can develop into cells of the innate and adaptive immune responses
Thymus: Where T cells are trained and learn not to react to the body.


What function do the spleen and lymph nodes play in the lymphatic system?

Lymph nodes are located along lymphatic vessels(which carry filtered lymph fluid from the blood and tissues. These are the sites where some immune responses are initiated (antigen carrying cells meeting T cells).
The spleen is the site of initiation for blood borne pathogens.


What are the three layers of immune defense?

1. Physical and chemical barriers (skin, mucosal membranes)
2. Arm 1: the innate immune system, a rapid non specific and fixed portion of the immune system.
3. Arm 2: The adaptive immune system, a slower highly specific and adapting portion of the immune system.


Compare the primary features of innate immunity and adaptive immunity

innate immunity is already in place when an infection starts and acts rapidly (within hours), it is fixed in what it can act on, not very specific and has no memory.
The adaptive immunity is essentially the opposite. Its function improves during the response, has a slow start time (days-weeks), is a highly variable and higly specific part of the immune system which can remember previous pathogens.


What does the memory function of the adaptive immunity mean?

You cannot be struck by the same pathogen twice.


How do vaccines work? What was the first example of this?

Vaccines work by stimulating the production of memory T cells for a specific disease without infecting the patient with that disease. The first example of this was the variolation done in china for smallpox, this took a controlled dose of the smallpox bacteria from the lesions it produced on the body.


What are phagocytes? What branch of the immune system are they from typically?

Phagocytes are cells which devour pathogens, They belong to the innate immunity branch of the immune system.


What is the molecule used to allow the immune system to recognise "self" cells and pathogens? What branch of the immune system is this from?

The Major histocompatability complex(MHC) complex, this is part of the adaptive immunity branch.


Why are diarrhea and vomiting useful defenses against infection?

Both of these functions will expel substances from the body, hopefully the pathogen will be taken with these lost substances.