WK 13 - Introduction to Immunology

Question 1

What is the purpose of immune system?

Answer 1

to protect hose from (potentially) dangerous non-self entities (e.g. infectious microorganisms)

Question 2

Define innate immunity.

Answer 2

defences that are not antigen-specific and that use mechanisms that exist before infection and are very rapid. Once our barriers (e.g. linings - skin) are breached by microbes, the innate system provides the initial defences.

Question 3

Define adaptive immunity.

Answer 3

defences that are antigen-specific and mediated by lymphocytes, B and T cells, following exposure to antigen. (a.k.a. acquired immunity)

Question 4

Define antigen.

Answer 4

any substance (usually foreign/non-self) that can elicit an adaptive immune response.

Question 5

Define antibody.

Answer 5

A glycoprotein that recognizes a particular antigen and facilitates clearance of that antigen. Antibodies are secreted by plasma cells. Plasma cells are the differentiated, effector cells derived from B cells.

Question 6

What is the early and non-specific response? Name four main cells involved.

Answer 6

Innate system.

natural killer cells, polymorphonuclear cells (neutrophils), macrophages, dendritic cells

Question 7

What is the later and specific response? Name the two main types of cells involved.

Answer 7

Adaptive System.
T cells, B cells –> plasma cells –> secretes antibodies [directs the hum oral response]
(dendritic cells also involved)

Question 8

How do cells of the immune system communicate?

Answer 8

cytokines

Question 9

Which leukocytes can produces cytokines?

Answer 9

all leukocytes can release cytokines, but may release only specific types of cytokines

Question 10

Which leukocytes can “receive” cytokines?

Answer 10

all leukocytes have receptors for cytokines

Question 11

What are cytokines and what are its functions?

Answer 11

Cytokines regulate the intensity and duration of the immune response by stimulating or inhibiting the activation, proliferation, and/or differentiation of various cells and by regulating the secretion of antibodies or there cytokines.

Question 12

What are interleukin (IL)?

Answer 12

The term “interleukin (IL)” is used with a number to designate a particular structurally-defined cytokine e.g. IL-2 is a cytokine produced by activated T-cells; it acts in an autocrine way to promote T-cell proliferation; it also acts in a paracrine way on nearby natural killer cells, T-cells and B-cells.

Question 13

How do immune system cells know and move to where the “problem” is?

Answer 13

chemotaxis

Question 14

What are chemotatic factor?

Answer 14

an agent that causes leukocytes to move up its concentration gradient. Chemokines, specific complement protein fragments, and certain bacterial peptides act as chemotactic factors.

Question 15

What are chemokine?

Answer 15

a type of cytokine that mediates chemotaxis and regulates expression of leukocyte adhesion molecules.

Question 16

Which of the following statements about cell communication is TRUE?

1. Neutrophils and macrophages respond to chemokines, but T cells do not.
2. Most cells of the innate & adaptive systems can produce cytokines.
3. Most leukocytes can respond to each & every different cytokine.

Answer 16

Statement 2

Question 17

What are phagocytic cells?

Name four phagocytic cells.

Answer 17

Phagocytic cells are cells that have the capacity to engulf and degrade a variety of microbes or particulate antigens.
Phagocytic cells include neutrophil, macrophage, dendritic cells, and monocytes. (Note: B cells are antigen specific and are not considered phagocytic cells)

Question 18

What are complement?

Answer 18

A system of (primarily) blood and cell membrane proteins that play multiple roles in host defines.

• a protein cascade system
• mostly in blood
• several effector functions aimed at killling microbes (esp. certain bacteria and to a lesser degree certain infected cells, certain tumour cells)
• involved in inflammation

Question 19

What activates the complement cascade system?

Answer 19

• antibody-antigen
• lectin
• alternative

Question 20

What is the purpose of activation of the complement through the 3 activation pathways?

Answer 20

to increase the ability to recognize pathogens

Question 21

What are the functions of complement effector?

Answer 21

1. complement activation fragments/peptides C5a and C3a are involved in inflammation
2. membrane attack complex forms a pore in target membranes
3. Opsonization

Question 22

Define opsonization.

Answer 22

the coating of targets with molecules for which the phagocyte has specific receptors. Opsonization greatly enhances phagocytosis. Certain complement activation products (e.g. C3b) are opsonins. They coat the target and are recognized and bound by complement receptors on the phagocyte surface. Antibodies are also opsonins.

Question 23

Name 3 professional antigen-presenting cells (APCs).

Answer 23

• macrophages
• DENDRITIC CELLS (MAJOR APC)
• B cells (restricted to Specific antigen)

Question 24

What do antigen-presenting cells do?

Answer 24

APCs internalize particles (e.g. bacteria), degrade them, and then stick particle bits (i.e. antigen) together with a particular protein that acts as an antigen - display molecule (called MHC) on their cell surface to show off to T lymphocytes.

Question 25

Which of the following statements about lymphocytes is TRUE?

1. B cells originate in the bone marrow and T cells originate in the thymus.
2. Lymphocytes are the most abundant subgroup of leukocytes, accounting for up to 70% of WBCs on a normal CBC.
3. Swollen lymph nodes during an infection are a consequence of proliferation of non-Ag-specific lymphocytes.
4. Most mature T cells are either Thelper Or Tcytotoxic cells.
5. Activated B cells differentiate into antibody-secreting plasma cells, but not into memory cells.

Answer 25

Statement number 4

Question 26

What are lymphocytes? Name the 2 types.

Answer 26

• subcategory of leukocytes
• are antigen-specific and have antigen-specific receptors
• exert their protective functions only after they have been activated
• the two types include T cells and B cells

Question 27

What does activation of lymphocyte requires?

Answer 27

• binding of specific antigen to the lymphocyte antigen receptor
• additional signals

Question 28

Describe what occurs after lymphocyte is activated.

Answer 28

1. Proliferate
   When an antigen binds to a B or T cells whose membrane-bound receptors are specific for that antigen (assume additional signals and requirements are provided), clonal expansion of that antigen-activated B or T cell occurs. All cells in the expanded clone are specific for that original antigen.
2. Differentiate
   Activated B cells differentiate into plasma cells, which produce and secrete antibodies. Activated T cells differentiate into effector cells with associated specific functions, depending on the T cell class. Some of the lymphocytes in the clone (~5%) differentiate into memory cells.

Question 29

What are the main antibody classes?

Answer 29

IgG, IgA, IgM, IgE & IgD (memory tool: GAMED)

Question 30

What is the main role of antibodies?

Answer 30

facilitate microbe destruction (e.g. destruction by phagocytosis), but do not directly act to destroy the microbe. (neutralization and opsonization)

Question 31

What are T helper lymphocyte cells (CD4+)?

Answer 31

activated T helper cells provide signals (e.g. cytokines) that promote immune responses.

Question 32

What are cytotoxic T lymphocyte cells (CD8+)?

Answer 32

CTL makes contact with a target cell (e.g. infected cell) displaying a specific antigen (together with a particular protein called MHCI). The CTL then induces the target cell to die by apoptosis.

Question 33

Which statement about the innate and/or adaptive systems is TRUE?

1. The innate system includes complement, macrophages, dendritic cells and T cells.
2. The antigen-presenting cells: macrophages and neutrophils, are innate system cells that display antigen to T cells.
3. The adaptive system provides an antigen-specific response and this happens after the innate response.
4. Cytokines are important for communication only between cells of the innate system.

Answer 33

Statement 3