1 - Basic concepts in Immunity

Question 1

Functions of the immune response

Answer 1

• Immunological recognition (innate and adaptive IR)
• Contain infection and if possible eliminate it (via antibodies)
• Immune regulation limits damage to host by immune response
• Generation of immunological memory by adaptive immune system

Question 2

4 levels of defence of protection

Answer 2

• Anatomic barriers (skin, oral mucosa)
• Compliment/antimicrobial proteins (C3, defensins)
• Innate immune cells (macrophages, NK cells, granulocytes)
• Adaptive immunity (B & T cells)

Question 3

Innate immunity

Answer 3

Mediated by mechanisms that are in place even before an infection occurs and facilitate rapid responses to invading microbes

Question 4

Innate immune cells

Answer 4

• Macrophages
• Dendritic cells
• NK cells
• Granulocytes

Question 5

Adaptive immune cells

Answer 5

• B lymphocytes
• Antibodies
• T lymphocytes
• Effector T cells

Question 6

Inflammatory response

Answer 6

• Bacteria trigger macrophages to release cytokines and chemokines
• Vasodilation and increased vascular permeability causes redness, heat and swelling
• inflammatory cells migrate into tissue, releasing the inflammatory mediators that cause pain

Question 7

Cardinal features of an adaptive immune response

Answer 7

Specificity, diversity, memory and self tolerance

Question 8

Determinants / epitopes

Answer 8

Parts of complex antigens that are specifically recognised by lymphocytes

Question 9

Clonal selection

Answer 9

Clones of lymphocytes with different specificities are present in unimmunised individuals, and are able to recognise and respond to foreign antigens

Question 10

Lymphocyte repertoire

Answer 10

The total number of antigenic specificities of the lymphocytes in an individual

Question 11

What causes the ability of the lymphocyte repertoire to recognise a large number of antigens

Answer 11

Variability in the structures of the antigen-binding sites of lymphocyte receptors for antigens.

Question 12

Difference between primary and secondary immune responses

Answer 12

Secondary immune responses and more rapid and greater in magnitude

Question 13

Why is the secondary response typically stronger

Answer 13

• Memory cells accumulate and become more numerous than the naive lymphocytes
• Memory cells react more rapidly and vigorously to antigen challenge compared to naive lymphocytes

Question 14

Mechanisms that maintain tolerance to self antigens

Answer 14

• Eliminating lymphocytes that express receptors specific for self antigens
• Inactivating self reactive lymphocytes
• Supressessing self reactive cells by actions of regulatory cells

Question 15

Stages of adaptive immune responses

Answer 15

• Antigen recognition
• Lymphocyte activation
• Antigen elimination
• Contraction (homeostasis)
• Memory

Question 16

Types of adaptive immunity

Answer 16

humoral and cell mediated

Question 17

Humoral immunity

Answer 17

B lymphocytes secrete antibodies that prevent infections and eliminate extracellular microbes

Question 18

Cell mediated immunity

Answer 18

Helper T lymphocytes activate macrophages and neutrophils to kill phagocytosed microbes, or cytotoxic T lymphocytes directly destroy infected cells

Question 19

Generative lymphoid organs

Answer 19

Bone marrow and thymus

Question 20

Secondary lymphoid organs

Answer 20

Lymph nodes, spleen, mucosal and cutaneous lymphoid tissues

Question 21

B lymphocyte lineage pathway

Answer 21

Bone marrow –> blood, lymph –> secondary lympoid organs

Question 22

T lymphocyte lineage pathway

Answer 22

• Bone marrow –> Thymus –> Blood, lymph –> secondary lymphoid organs.
• Some immature B cells leave bone marrow and complete maturation in the spleen

Question 23

Active immunity

Answer 23

• Caused by a host response to a microbe or antigen
• Generates immunologic memory

Question 24

Passive immunity

Answer 24

Caused by transfer of antibodies or T lymphocytes specific for the microbe (e.g. from mother to fetus, vaccine)

Question 25

Herd immunity

Answer 25

- Occurs when a large portion of a community becomes immune to a disease, making spread unlikely - Whole community becomes protected

Question 26

Immune diseases examples

Answer 26

- Rheumatoid arthritis - Allergy - Lupus - Hypothyroidism - Coeliac disease

Question 27

Why was smallpox able to be eradicated

Answer 27

- DNA virus that doesn't change very much - No animal reservoirs

Question 28

What are the two major subsets of lymphocytes

Answer 28

B and T cells

Question 29

Explain adaptive immune response

Answer 29

- Specialised APCs recognise and capture microbial antigens, and display these antigens for recognition by lymphocytes - Lymphocytes proliferate and differentiate into effector cells - Effector cells eliminate the antigen and turn into memory cells

Question 30

Only cells capable of specifically recognising antigens

Answer 30

- Lymphocytes - Therefore principle cells of adaptive immunity