Non-specific Defense, Immunity and Autoimmunity

Question 1

What are the three layers of a non-specific defense system?

Answer 1

• Barriers
• Chemical
• Cells (macrophage, etc)

Question 2

Antigen vs antibody

Answer 2

• Antigen - agent that geneate antibody - foreign protein that triggers the immune system

Question 3

Difference between T cell and B cell

Answer 3

• B cells are responsible for humoral immune response.
• T cells are responsible for cell-mediated immune response.

T cells vs B Cells T cells and B cells are the two types of lymphocytes that are involved in triggering the immune response in the body. Both T cells and B cells are produced in the bone marrow. The T cells migrate to the thymus for maturation. Both T cells and B cells are involved in recognizing pathogens and other harmful, foreign materials inside the body such as bacteria, viruses, parasites, and dead cells. The two types of T cells are helper T cells and cytotoxic T cells. The major function of the helper T cells is to activate cytotoxic T cells and B cells. The cytotoxic T cells destroy pathogens by phagocytosis. B cells produce and secrete antibodies, activating the immune system to destroy the pathogens. The main difference between T cells and B cells is that T cells can only recognize viral antigens outside the infected cells whereas B cells can recognize the surface antigens of bacteria and viruses.

Question 4

MHC 1 vs MHC II

Answer 4

• found on all cells displaying the cell contents.
• Killer T cells.

MHC class I molecules are one of two primary classes of major histocompatibility complex (MHC) molecules (the other being MHC class II) and are found on the cell surface of all nucleated cells in the bodies of vertebrates. They also occur on platelets, but not on red blood cells.

MHC II are found on cells that digest the antigent presenting cells such as macrophages, phagocytes, B cells

Question 5

Killer vs helper T cell

APC stands for?

Answer 5

• Killer T cell kills while helper T cell help amplify the immune response by looking for signs of invaders on the MHC II.
• MCH II is only displayed by macrophages.
• T cells cannot bind directly to antigens thus requires an alternative mechanism of interaction.
• Every T cells have receptors called T Cells Receptors (TCR) and a helper protein that assists with the binding of the Major Histo-compatibility Complexes I & II.
• If a T cell has a CD4 on in –> helper T cell.
• If a T cell has a CD8 on it –> killer T cell (8 = eat = kill)
• Helper T cells can only bind to MHC II, which are displayed on the macrophages. T cells help amplify the immune response.

APC - antigen presenting cells

Question 6

Primary and secondary responses

Answer 6

• memory cells allow for faster and stronger secondary responses after the initial exposure or infection.

Question 7

What immunity?

Answer 7

• Targeted attack of invaders. very costly.

Question 8

Two branches of the adaptive immune system

Answer 8

• Humoral immunity - B cells produce and secrete antibodies into the bloodstream.
• The extracellular spaces are protected by the humoral immune response, in which antibodies produced by B cells cause the destruction of extracellular microorganisms and prevent the spread of intracellular infections.
• Cell-mediated immunity

Question 9

How many types of antibodies does a single B cell produce?

Answer 9

Each B cell only makes one type of antibody.
They are highly specialized cells.

• B cell has the antibody it produces on the surface. It acts as an antigen receptor. The B cell only produces the antibody when the antigen binds to the antibody on the surface.
• B cell clones themselves so they can produce antibodies rapidly.

Question 10

T cells - Cell-mediated immunity

How many types of T cells are there? what are they?

Answer 10

• The killer T Cell and the helper T cell.

- The T cell will kill any foreign cells, but how can T cell tell what cells are invaders?

Question 11

How do killer T cells know which cell to kill?

Answer 11

MHC 1 – found on call cells and allows cells to display cell contents on the surface.

Question 12

What do helper T cells do?

Answer 12

Their name says it all. They don’t actually do the killing. They send signals so the B cells and the killer T cells can proliferate, magnify the immune response whenever it runs into a foreign cell. How does it recognize that?

Question 13

Autoimmunity – what is this?

Answer 13

• Immune systems attack host cells.

Question 14

How to prevent autoimmunity? Well in short, you have to make sure that those cells that attack the host cells are destroyed before they are released into circulation.

Answer 14

T cells and B cell are produced randomly, but they have to go through a vetting process before being released into the circulation.

This is to make sure that they do not regcognize any self thing. All the B cells and T cells that do bind to self things are either deactivated (if it’s just soluble protein) or killed (bind to cell-surface protein)

– Any T and B cells that don’t recognize any self thing are then released into circulation.

The destruction of B cell is in the bone narrow wherease T cell is in the thymus.

Question 15

How to prevent autoimmunity? Well in short, you have to make sure that those cells that attack the host cells are destroyed before they are released into circulation.

Answer 15

T cells and B cells are produced randomly, but they have to go through a vetting process before being released into circulation.

This is to make sure that they do not recognize any self thing. All the B cells and T cells that do bind to self things are either deactivated (if it’s just soluble protein) or killed (bind to cell-surface protein)

– Any T and B cells that don’t recognize any self thing are then released into circulation.

The destruction of B cell is in the bone marrow whereas T cell is in the thymus.

Question 16

What are non-specific defenses that makeup Innate Immunity?

Answer 16

• First line of defense - the physical and chemical barriers. (skin, stomach acid, mucus, oil skins,etc)
• The second line of defense - the inflammatory response. (blood flow, phagocytes, increase in body temperature, etc)

-An inflammatory response begins when a pathogen stimulates an increase in blood flow to the infected area. Blood vessels in that area expand, and white blood cells leak from the vessels to invade the infected tissue. These white blood cells, called phagocytes engulf and destroy bacteria. The area often becomes red, swollen, and painful during an inflammatory response.
When a pathogen has invaded, the immune system may also release chemicals that increase body temperature, producing a fever. Increased body temperature may slow or stop pathogens from growing and helps speed up the immune response.

Question 17

Why are the lymphocytes named B and T cells?

Answer 17

• They are both produced at the bone marrow but T cells mature in the Thymus.

Question 18

Which cells produce antibody and what do antibodies do?

Answer 18

Specific immune responses are triggered by antigens. Antigens are usually found on the surface of pathogens and are unique to that particular pathogen. The immune system responds to antigens by producing cells that directly attack the pathogen, or by producing special proteins called antibodies. Antibodies attach to an antigen and attract cells that will engulf and destroy the pathogen.

Question 19

What roles do B Cells and helper T cells do in Humoral response?

Answer 19

Humoral immunity relies on the actions of antibodies circulating through the body.

Humoral immunity begins when an antibody on a B cell binds to an antigen. The B cell then internalizes the antigen and presents it to a specialized helper T cell, which in turn activates the B cell.
Activated B cells grow rapidly, producing plasma cells, which release antibodies into the bloodstream, and memory B cells, which store information about the pathogen in order to provide future immunity.

Question 20

what happens in cell-mediated immune response?

Answer 20

Antibodies alone are often not enough to protect the body against pathogens. In these instances, the immune system uses cell-mediated immunity to destroy infected body cells.

T cells are responsible for cell-mediated immunity. Killer T cells (cytotoxic T cells) assist with the elimination of infected body cells by releasing toxins into them and promoting apoptosis. Helper T cells act to activate other immune cells.