Immune evasion

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Home assignment 5

Immune Evasion

BIO3124 Case Study

Professor:

Group #33:

Questions

Charlie created a chart in order to keep track of the arms of the immune system so that he could figure out how

his body would keep him healthy. Complete the chart with respect to the key hallmarks of the innate and adaptive responses. It is okay to look this information up in a text or on the internet. (1 point for each box, no need to elaborate answers needlessly, 14 points in total)

Hallmark	Innate	Adaptive
Level of specificity	non specific	Highly specific
Involvement of memory	No memory retained of previous infections	retains memory of previous infections (Previous pathogens can be recognized by T cells which have a “memory”)
Time for first response to an antigen	immediate/fast response (minutes to hours)	slow response (1-2 weeks)
Time for secondary/repeated response to an antigen	fast (same response as first)	faster response than first response
Level of self discrimination	good at attacking only non-self pathogens because it has high level of self discrimination and non-self discrimination	Not very good at self discrimination because it sometimes attacks itself resulting in autoimmune diseases.
Duration of the response	short	long lasting
Key cells involved	neutrophiles, macrophages, Natural Killer cells, dendritic cells, eosinophils, mast cells, basophils, phagocytes	T cells, B cells and other antigen presenting cells

Anatomical barriers play a large role in preventing the entrance of a pathogen into the body. They provide a critical first line of defense. Think about what a potential pathogen like a bacteria or a virus would have to overcome in order to get into your body, or Charlie’s body, and then into the target tissue to untimely make you sick. List several (at least three) of these critical barriers and how they help to eliminate pathogens. Describe how

these mechanisms are or could be related to the symptoms you often get when someone falls ill (for example with the cold or a stomach flu). (4 point for each example, 12 points in total)

Containing white blood cells, blood is a very critical barrier to pathogens. As pathogens invade the body, the number of white blood cells increases, they multiply to destroy the bacteria or virus that entered the body. They get directed towards the site of the infection to fight the invading pathogen.

The skin is one of the most significant immunological barriers that isolate the “inside” of the body from the “outside”. The skin provides an important physical barrier as it prevents microbes from reaching tissues that are susceptible to infection. The skin is composed of 3 layers of cells that are tightly packed together; the epidermis, the dermis, and the hypodermis. The tightly packed cells of these layers will make it extremely difficult for microbes to get to deeper tissues of the body and infect them. When the skin barrier is broken (a wound for example) microbes can enter the body through the “openings” in the skin layers and will be able to infect different body tissues. Also, the endothelia, which are epithelial cells that line blood vessels, lymphatic vessels, and other tissues, play a crucial role in protecting the central nervous system from infections.

Mucous membranes are another important physical barrier that protects against pathogens. Mucous membranes line the mouth, nose, lungs, digestive and urinary tracts. They consist of epithelial cells which secrete mucus. The mucus traps microbes and other small particles in the air and also contains antimicrobial substances. The body then gets rid of the mucus in different ways depending on the different regions of the body and it gets rid of the trapped microbes, dust particles, and other small particles along with the mucus. For example, the body gets rid of the mucus layer that line parts of the respiratory tract along with its trapped microbes and dust particles as phlegm through coughing or sneezing. The body is protected from many potential pathogens by these mucous membranes that prevent the pathogens from getting to body tissues that are potential target for infectious microbes.

Questions

It is clear that the innate and adaptive arms of the immune response work interdependently to clear pathogens, however key cells also play vital roles in each arm of the response. Help Charlie keep the working parts straight

by filling in the chart below. Indicate a role for the following cells and whether they are key players in the innate or adaptive arm of the immune response. (1point for each box, some answers need a couple or a few of sentences to have sufficient accuracy or information to be correct, but 1 or 2 sentences mostly sufficient)

Cell Type	Role During an Infection (Identify the effector mechanism employed by the cells to stop infection)	Arm of the Response (Innate or Adaptive)
Macrophage	It is a large white blood cell that is phagocytic, which means it engulfs, processes and destroys pathogens by phagocytosis. Macrophages also release molecules known as cytokines which trigger other cells to initiate a defensive response.	Innate
NK cell	Natural killer cells are a type of white blood cells that has a major role in protecting the body from tumours and viral infections. They are cytotoxic which means they’re capable of apoptosis which leads to the destruction of viruses inside a cell. They are activated in response to macrophage-derived cytokines. finds and kills compromised cells ?!	Innate
B cell	A type of white blood cells that make antibodies which trap specific viruses and bacteria. They have BCRs on their cell membrane which allow them to bind to a specific antigen. They are memory cells which means that if the same pathogen invades the body a second time in the future, B cells will recognise it faster and will be more ready to trap it produce antibodies	adaptive
T cell	A type of lymphocytes that originates from the thymus gland. They have TCRs on the cell surface which bind to antigens. When helper T cells are stimulated by binding to an antigen, T cells secrete cytokines which in turn stimulate differentiation of B cells. Other T cells bind to and kill cancer cells and infected cells help^[a]^[b]^[c]^[d]^[e] B cells to make antibodies. recognise and kill viruses	adaptive
Mast cell	Found in connective tissues, they contain basophil granules, and they release histamine, heparin cytokines and other substances. They respond to certain pathogens and they release chemicals during allergic reactions. initiates inflammatory response through degranulation	innate
Dendritic cell	They link the innate and adaptive arms of the immune system They are antigen-presenting cells (APCs) meaning that they recognise pathogens by recognizing antigens and they initiate immune response based on that. They are also phagocytes Trigger the initiation of primary T-cell responses They play major roles in the initiation of adaptive immune responses. ingest antigens	Both
Neutrophil	Most abundant type of white blood cells (they make up 55-70% of white blood cells) They are a type of granulocyte (containing granules) and a type of phagocytes Neutrophils are one of the first responders to go to the sites of infection and eat up the forgein invaders (phagocytosis). After they take them up they treat them with enzymes that destroy them sense presence of an infection	Both
Eosinophils	a proinflammatory white blood cell that are anti-parasitic, have bactericidal activities, kill cells, and participate in allergic reactions destroy foreign substances and regulate inflammation	Innate

What is antigen presentation and why is it critical during an immune response? (3 points)

Antigen presentation is a process where antigen is presented to lymphocytes such as T cells. Therefore, the receptors on the T cells will recognise and bind to the fragments of the antigens. The antigens- presentation is an important process to enhance the recognition of antigens by the T-cells. It is a way where the host can develop memory to pathogens. This antigen interaction with the T-cell will improve the immune response and the recognition of antigen by the T-cells.

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