adaptive immunity

Question 1

When is adaptive immunity activated?

Answer 1

When the innate immune response is insufficient to control an infection

Question 2

Is adaptive immunity immediate?

Answer 2

No, it takes several days

Question 3

What are the 2 types of adaptive responses and what cells are they controlled by?

Answer 3

1. cell-mediated: carried out by T cells

2. humoral immune response: controlled by activated B cells & antibodies

Question 4

Adaptive immunity also involves a _____ to provide the host with __________ from reinfection with the same type of pathogen

Answer 4

memory;

long-term protection

Question 5

Antigen recognition is mediated by specific ________ which bind to antigens or are derived from pathogens.

Answer 5

antigen receptors

Question 6

The challenge for T lymphocytes

Answer 6

Very few lymphocytes in the body are specific for any 1 antigen:

• specificity & diversity of antigen receptors
• frequency of antigen responsive lymphocytes

Question 7

T cells NEVER bind to _____ in their native configuration.

T cells that bind to antigens from bacteria and viruses NEVER come in direct contact with the bacteria or virus.

Answer 7

antigens

Question 8

T- cell receptors bind to a) ______ derived from foreign proteins.
The a)______ must be presented to T cells by b) ______________ encoded molecules.

Answer 8

a) peptides

b) Major Histocompatibility Complex (MHC)

Question 9

Dendritic cells travel via circulation to lymph nodes. Once they arrived there, they start to present their antigens to ________ within ____ complexes on their cell surfaces.

Answer 9

naive T helper cells within MHC II

Question 10

Naive cells are mainly found in ______ and _____

Answer 10

lymph nodes and spleen

Question 11

List the antigen presenting cells (APCs)

Answer 11

dendritic cells
B cells
macrophages
Langerhans cells

Question 12

Functions of APCs
1. Capture _______ & take them to the “correct” place (to the ______________, through whr naive lymphocytes circulate)

2. Display _______ in a form that can be recognised by ______________
3. Provide _______ for ______________ (cytokines induced by microbes– ensure that T cells respond best to microbial antigens)

Answer 12

1. Capture antigens & take them to the “correct” place (to the peripheral/secondary lymphoid organs, through whr naive lymphocytes circulate)
2. Display antigens in a form that can be recognised by specific T lymphocytes (MHC)
3. Provide “2nd signals” for T cell activation (cytokines induced by microbes– ensure that T cells respond best to microbial antigens)

Question 13

MHC is also called _________

Answer 13

human leukocyte antigens (HLA)

Question 14

Antigen receptors of T cells have dual specificities:
1.
2.

Answer 14

1. For peptide antigen (responsible for specificity of immune response)
2. For self MHC molecules (responsible for MHC restriction)

Question 15

T- cells learn self MHC restriction during ___________

Answer 15

development in the thymus

Question 16

Antigen processing: conversion of 1. _______ (globular protein) into 2. ______ capable of binding to MHC molecules by 3. ________

Answer 16

1. native antigen
2. peptides
3. proteolytic cleavage

Question 17

1. _____ antigens are displayed by MHC I

2. _____ antigens are displayed by MHC II

Answer 17

1. intracellular

2. extracellular

Question 18

T-cell activation requires 2 signals.
Both signals are provided by activated APCs:
Signal 1:
Signal 2:

Answer 18

Signal 1: peptide-MHC

Signal 2: costimulatory molecules & cytokines

Question 19

Effector CD4+ T cells activate __________

Answer 19

macrophages, B cells, cytotoxic T cells, etc

Question 20

Mature naive B cells expressing 1. __________ exit bone marrow and migrate to 2. ________.

They recirculate and enter B cell follicles in lymph nodes & spleen responding to 3. ________ and _____.

Answer 20

1. surface immunoglobulin (BCR)
2. secondary lymphoid organs
3. antigen encounter with T cell help & proliferating

Question 21

Activated B cells differentiate into 1. ________ which produce 2. _____ or ______.

Answer 21

1. plasma cells

2. antibodies or memory B cells

Question 22

Fragment antigen binding (Fab) region binds to _______ & interferes with their _____________.

Answer 22

binds to microbes & toxins

interferes with their ability to interact with cells

Question 23

Fragment crystallisable (Fc) region activates 1. ______ in the immune cells that express Fc receptors (eg. phagocytosis) and 2. ______.

Answer 23

1. effector function

2. complement

Question 24

List some effector functions

Answer 24

1. Neutralisation
2. Complement activation
3. Opsonisation
4. ADCC
5. Inflammation
6. Lysis of microbes

Question 25

B-cell activation depends on T cell.
Requires 2 signals:
Signal 1:
Signal 2:

Answer 25

Signal 1: binding of native antigen to surface lgM/lgD on naive follicular B cell
- B cell internalises antigen & presents peptide-MHC II to antigen-specific effector T helper cell = antigen specific T cell- B cell interaction

Signal 2: T cell receptor triggering up-regulates on costimulatory molecule, CD40L, on T cell & CD40 signaling promotes B cell activation

Question 26

Define isotypes:

Answer 26

immunoglobulins with the same antigen specificity (same variable region) but different constant regions

Question 27

Upon isotype switching, antibodies retain the same ________, but have different ______.

Answer 27

the same antigen specificity;

but different effector functions

Question 28

Isotype switching is dependent on _______ in the form of ____

Answer 28

dependent on T cells in the form of CD40L

Question 29

Purpose of isotype switching

Answer 29

diversifies the functional properties of the antibody (Fc region)

Question 30

Are memory B cells longer lived than naive b cells?

Why?

Answer 30

Yes

The persistence of memory B cells after an immune response ensures that we have increased no. of B cells specific for antigen and ready to respond on re-encounter

Question 31

In humoral immunity, ___ lymphocytes secrete _____ that eliminate extracellular microbes.

Answer 31

B lymphocytes secrete antibodies

Question 32

In cell-mediated immunity, __ lymphocytes either activate _________ to destroy phagocytosed microbes, or kill _________. ___ lymphocytes also provide a helper function for __ cells.

Answer 32

T lymphocytes either activate macrophages to destroy phagocytosed microbes, or kill infected cells. T lymphocytes also provide a helper function for B cells.

Question 33

1. CD4 T cells recognise MHC ___ + peptide

2. CD8 T cells recognise MHC ___ + peptide

Answer 33

1. II

2. I