Immunology basics

Question 1

Where does the immune system come from?

Answer 1

The bone marrow and the thymus. The cells are made in the bone marrow, B lymphocytes mature in the bone marrow and T lymphocytes mature in the thymus. Immune cells can also remain in the spleen and lymph system until activated.

Question 2

What is an antigen?

Answer 2

Any substance that is able to cause an immune response in the body, e.g., bacteria.

Question 3

What are antigen presenting cells?

Answer 3

Cells, such as macrophages, dendritic cells and B cells, that can process protein antigens into peptides. These peptides can then be presented (along with major histocompatibility complex) to T-cell receptors on the surface of the cell.

Question 4

What is an antibody?

Answer 4

Special proteins created by white blood cells that can kill or weaken infection-causing organisms, also called immunoglobulin.

Question 5

What cells are produced by the myeloid lineage?

Answer 5

RBC
Platelets
Myeloblasts (eosinophils, basophils, neutrophils, monocyte)
Monocytes become macrophages

Question 6

What cells are produced by the lymphoid lineage?

Answer 6

Lymphoblast (natural killer cells, B lymphocytes, T lymphocytes)
B lymphocytes become memory B cells and plasma B cells
T lymphocytes become cytotoxic T cells, helper T cells, memory T cells, regulatory T cells

Question 7

What is a basophil?

Answer 7

A basophil is a type of phagocytic immune cell that has granules. Inflammation causes basophils to release histamine during allergic reactions.

Question 8

What is a B lympocyte?

Answer 8

A B lymphocyte is a type of white blood cell that develops in the bone marrow and makes antibodies.

Question 9

What are B memory cells?

Answer 9

B cells that are long lived and remember past antigen exposure.

Question 10

What are plasma B cells?

Answer 10

Activated B cells that produce antibodies. Only one type of antibody is produced per plasma B cell.

Question 11

What are cytokines?

Answer 11

A type of protein that impacts the immune system by either ramping it up or slowing it down. Cytokines can occur naturally in the body or be produced in a laboratory.

Question 12

What is a dendritic cell?

Answer 12

Dendritic cells are antigen-presenting cells (APCs). Antigen is combined with major histocompatibility complex and presented on a dendritic cell to active T and B lymphocytes.

Question 13

What is an eosinophil?

Answer 13

An eosinophil is a type of immune cell (leukocyte, or white blood cell). They help fight infection or cause inflammation.

Question 14

What are granulocytes?

Answer 14

Granulocytes (including eosinophils, neutrophils and basophils) are a type of white blood cell that releases toxic materials, such as antimicrobial agents, enzymes, nitrogen oxides and other proteins, during an attack from a pathogen.

Question 15

What is the major histocompatibility complex?

Answer 15

MHC is a group of genes that code for proteins on the cells of the immune system. Referred to as the human leukocyte antigen (HLA) system in humans.

Question 16

What is the human leukocyte antigen?

Answer 16

Human version of the major histocompatibility complex (MHC). The MHC complex is a family of 200+ genes categorized into three classes: I, II, III.

Class I genes make proteins that are located on the surface of almost all cells.
Class II genes are located on the surface of immune cells.
Class III genes are also involved with the immune system and inflammation.

Question 17

What are natural killer cells?

Answer 17

The primary effector cell of innate immunity; the first responders of the immune system. They interact with signals from other cells (activating and inhibitory).

Question 18

What are T cells?

Answer 18

Type of white blood cell that is involved with the immune system. T lymphocytes mature in the thymus and differentiate into cytotoxic, memory, helper and regulatory T cells.

Question 19

What are cytotoxic T cells?

Answer 19

Cytotoxic T cells are the primary effector cells of adaptive immunity. Activated cytotoxic T cells can migrate through blood vessel walls and non-lymphoid tissues. They can also travel across the blood brain barrier. Cytotoxic T cells are activated by cytokines. They can attach to cancer cells and kill them.

Question 20

What are memory T cells?

Answer 20

Derived from activated cytotoxic T cells, memory T cells are long-lived and antigen-experienced. One memory T cell can produce multiple cytotoxic T cells. After activated cytotoxic T cells attack the pathogen, the memory T cells hang around to mitigate any recurrence.

Question 21

What are helper T cells?

Answer 21

Helper T cells secrete cytokines that help B cells differentiate into plasma cells. These cells also help to activate cytotoxic T cells and macrophages.

Question 22

What are regulatory T cells?

Answer 22

Regulatory T cells (or Tregs) help to suppress the immune system.

Question 23

What are lymphocytes?

Answer 23

Lymphocytes are immune cells found in the blood and lymph tissue. T and B lymphocytes are the two main types.

Question 24

What is a macrophage?

Answer 24

Macrophages are large white blood cells that reside in tissues that specialize in engulfing and digesting cellular debris, pathogens and other foreign substances in the body.

Question 25

What are mast cells?

Answer 25

Mast cells release histamine and help to get rid of allergens.

Question 26

What are monocytes?

Answer 26

Large white blood cells that reside in the blood stream that specialize in engulfing and digesting cellular debris, pathogens and other foreign substances in the body. Monocytes become macrophages.

Question 27

What are myeloid derived suppressor cells?

Answer 27

When immature myeloid cells cannot differentiate into mature myeloid cells, due to conditions like cancer, expansion of myeloid-derived suppressor cells occurs, and the T-cell response can be suppressed.

Question 28

What is a neturophil?

Answer 28

A type of white blood cell, granulocyte, and phagocyte that aids in fighting infection. Neutrophils kill pathogens by ingesting them.

Question 29

What are phagocytes?

Answer 29

Phagocytes eat up pathogens by attaching to and wrapping around the pathogen to engulf it. Once the pathogen is trapped inside the phagocyte, it is in a compartment called a phagosome. The phagosome will then merge with a lysosome or granule to form a phagolysosome, where the pathogen is killed by toxic materials, such as antimicrobial agents, enzymes, nitrogen oxides or other proteins.

Question 30

What are the cells of the innate immune system?

Answer 30

Natural killer cells, macrophages, neutrophils, dendritic cells, mast cells, basophils, eosinophils.

Question 31

What are the cells of the adaptive immune system?

Answer 31

T and B lymphocytes.

Question 32

What is the purpose of inflammation?

Answer 32

Inflammatory response plays a critical role in immunity. When tissues are damaged, the inflammatory response is initiated, and the immune system becomes mobilized. The immune cells of the innate immune system (i.e., neutrophils and eosinophils) are the first recruited to the site of tissue injury or damage via blood vessels and lymphatic system, followed by macrophages.

1. Prevent initial establishment of infection or remove damaged tissue.
2. Prevent the spread of infection or repair damaged tissue.
3. Recruit effector cells if the immune cells of the innate immune system cannot control infection or repair damaged tissue.
4. Mobilize effector cells (T and B lymphocytes).

Question 33

What are the two immunity methods within adaptive immunity?

Answer 33

Cellular and humoral immunity.

Question 34

What is humoral immunity?

Answer 34

Humoral immunity is also called antibody-mediated immunity. With assistance from helper T cells, B cells will differentiate into plasma B cells that can produce antibodies against a specific antigen. The humoral immune system deals with antigens from pathogens that are freely circulating, or outside the infected cells. Antibodies produced by the B cells will bind to antigens, neutralizing them, or causing lysis (dissolution or destruction of cells by a lysin) or phagocytosis.

Question 35

What is cellular immunity?

Answer 35

Cellular immunity occurs inside infected cells and is mediated by T lymphocytes. The pathogen’s antigens are expressed on the cell surface or on an antigen-presenting cell. Helper T cells release cytokines that help activated T cells bind to the infected cells’ MHC-antigen complex and differentiate the T cell into a cytotoxic T cell. The infected cell then undergoes lysis.

Question 36

What is anergy?

Answer 36

Anergy, or immune intolerance, occurs when the there is a failure to mount a complete immune response to an antigen. Anergy can occur in both T and B lymphocytes.