CH1 - Intro to the immune system

Question 1

What is the function of the immune system?

Answer 1

Protect individuals against infections and cancer

Question 2

What is innate immunity?

Answer 2

• early line of defence

- mediated by cells and microbes that are always present and ready to eliminate

Question 3

What are lymphocytes?

Answer 3

• cells of adaptive immunity

- only cells which clonally distribute receptors specific for different antigens

Question 4

What is humoral immunity?

Answer 4

antibodies neutralise and eradicate extracellular microbes and toxins

Question 5

What is cell-mediated immunity?

Answer 5

T lymphs eradicate intracellular microbes

Question 6

What is adaptive immunnity?

Answer 6

- humoral and cell-mediated
Phases:
   - antigen recog by lymphs
   - activation of lymphs to proliferate (rapid increase) and differentiate into effector and memory cells
   - elimination of microbes
   - decline of immune response
   - long-lived memory

Question 7

Which type of cells are the only cells to produce antibodies?

Answer 7

B lymphocytes

- they express membrane antibodies that recognise antigens

Question 8

What are the descendants of activated B cells?

Answer 8

Plasma cells

Question 9

What do plasma cells do?

Answer 9

secrete antibodies neutralising and eliminating the antigen

Question 10

What do T lymphocytes do?

Answer 10

recognise peptide (building blocks of protiens) fragments of protein antigens displayed on other cells

Question 11

What do helper T lymphocytes do?

Answer 11

produce cytokines that activate phagocytes to destroy ingested microbes, recruit leukocytes and activate B lymphs to produce antibodies

Question 12

What do cytotoxic T lymphocytes (CTLs) do?

Answer 12

• kill infected cells harbouring microbes in the cytoplasm

Question 13

What do Antigen Presenting Cells (APC) do?

Answer 13

capture antigens of microbes that enter through epithelia, concentrate them in lymphoid organs and display these antigens for recognition by T cells

Question 14

Where are lymphocytes and APCs organised?

Answer 14

in peripheral (2ndary) lymphnoid organs

Question 15

Where are immune responses initated and developed?

Answer 15

Secondary lymphoid organs such as

  - lymph nodes (LNs)
  - spleen
  - Peyer's patches (PPs) and mucosal tissues- the nasal associated lymphoid tissue (NALT), adenoids, and tonsils.

Question 16

Where do naïve lymphocytes circulate?

Answer 16

peripheral lymphoid organs –> to search for foreign antigens

Question 17

What is the role of effector t lymphocytes?

Answer 17

eliminate infectious microbes at peripheral (near surface) sites of infection

Question 18

What is the role of plasma cells and where are they located?

Answer 18

Secrete antibodies that enter circulation, finding and eliminating microbes

They remain in lymphoid organs and bone marrow

Question 19

Q - What are the two types of adaptive immunity, and what types of microbes do these adaptive immune responses combat?

Answer 19

Humoral and cell mediated

Humoral: extracellular microbes and toxins

Cell Mediated: intracellular microbes

Question 20

Q - What are the principal classes of lymphocytes, and how do they differ in function?

Answer 20

T and B cells

T cells: mediators of cell-mediated immunity

B cells: mediators of humoral immunity

Question 21

Q - What are the important differences among naïve, effector and memory T and B lymphocytes?

Answer 21

Naive cells are mature T or B cells that have not been activated by an microbe antigen yet. They pass through the circulation in lymph nodes or wait in the tissue for a breach.

Effector cells have been activated in some way by the presence of a pathogen. These cells elicit an antimicrobial defense to protect or eliminate pathogens. Most effector cells die after some time, but some live on.

B cells - secrete antibodies that bind to antigens, or initiate the complement system,

T cells - recognize, ingest and destroy microbes, display their peptides to B cells activating their humoral response

Memory B cells live on after the immune response dies down. They can change isotopes of antibody immunoglobulin to improve affinity and specialize for particular antigens. Improve reaction to second exposure.

Question 22

Where are T and B lymphocytes located in the lymph nodes and how is their anatomic separation maintained?

Answer 22

B: mature in bone marrow
T: mature in thymus

T and B cells initially enter the same region of a lymph node but are then attracted by different chemokines to separate regions of the node

Question 23

How do naïve and effector T lymphocytes differ in their patterns of migration?

Answer 23

• Naive LCs circulate through the peripheral lymphoid organs searching for foreighn antigens. - Effector T-LCs migrate to peripheral sites of infection and eliminate infectious microbes.