Lecture 1 - Introduction to Immunology

Question 1

Define Immunology

Answer 1

The study of all aspects of Host Defence against Infection

Question 2

What are the Two Types of Lymphoid Organs (Give Examples)?

Answer 2

• Primary e.g., Bone Marrow, Thymus
• Secondary e.g., Spleen, Lymph nodes, Appendix

Question 3

What are the Three Types of Cellular Constituent in the blood?

Answer 3

• Erythrocytes (RBC’s)
• Leukocytes (WBC’s)
• Thrombocytes (Platelets)

Question 4

Define the Two Phases of Host Immune Defences

Answer 4

• Innate Immunity - pre-existing initial protection against infection
• Adaptive Immunity - adapts to specific pathogens and mediates later defence against infection

Question 5

How can Myeloid Leukocytes be divided?

Answer 5

• 60-70% Granulocytes
• 30-40% Monocytes

Question 6

Where do Myeloid cells complete their development?

Answer 6

Bone Marrow and Blood (No Secondary Lymph Organs)

Question 7

Where do Lymphoid cells complete their development?

Answer 7

Lymphoid Organs (e.g., Bone Marrow, Spleen, Thymus)

Question 8

Define the 4 main types of Lymphoid cells

Answer 8

• T-Lymphocyte
• B-Lymphocyte
• Natural Killer (NK) cell
• Dendritic cell (Lymphoid Lineage)

Question 9

Describe the steps of an adaptive immune response

Answer 9

1. Antigens in local lymphoid tissue activate APCs (e.g., Dendritic Cells)
2. Antigens presented on APC activate lymphocytes with complementary receptors to recognise specific pathogen proteins
3. Antigen-specific Lymphocytes undergo clonal expansion, producing many effector cells via differentiation

Question 10

State what happens to the two major classes of naïve lymphocyte

Answer 10

• Naïve B Lymphocytes - differentiate into plasma cells once activated, which secrete antibodies in the bone marrow (Humoral Immunity)
• Naïve T Lymphocytes - mature in thymus, differentiate into effector T-cells once activated (Cell-Mediated Immunity)

Question 11

Describe the development of Lymphocytes

(From Birth to Activation)

Answer 11

1. Lymphocytes arise from Haematopoietic Stem Cells (HSCs), which mature in either the Thymus or Bone Marrow
2. Mature Lymphocytes are carried in the vasculature to secondary lymphoid organs, the site of activation
3. Lymphocytes circulate between the blood and lymphatic system until they encounter their specific antigen

Question 12

How is an Infection resolved?

(2 Points)

Answer 12

• Removal of Effector cells by Apoptosis to restore tissue integrity
• Retention of some effector cells to provide memory responses to future infections (Memory B/T cells)

Question 13

What is required for Effective Protective Immunity?

Answer 13

Requires pre-existing antibodies/cells to allow more efficient and rapid response to pathogen re-exposure

Question 14

What is Vaccination? What can a vaccine consist of?

Answer 14

• Deliberate induction of the adaptive immune response to produce long-term immunity for specific pathogen
• Dead/Attenuated form of pathogen
• Pathogenic proteins
• Nucleic acids

Question 15

Describe the Clonal Selection Hypothesis?

(3 Points)

Answer 15

• Each Lymphocyte bears a single type of receptor with unique specificity
• High Affinity interactions between foreign molecule and receptor leads to activation of lymphocyte
• An Activated Lymphocyte will divide to produce differentiated effector cells bearing receptors of identical specificity to parent (not entirely true)

Question 16

How is Self-Reactivity Prevented?

Answer 16

Lymphocytes bearing receptors specific for ubiquitous self molecules are deleted at early stage in lymphoid development

Question 17

Why do Lymphocytes require co-stimulation for activation?

Answer 17

It is a safeguard against accidental activation of B/T-lymphocytes