Immunology 2 - Immune Cells and Organs

Question 1

What are primary lymphoid organs?

Answer 1

• Organs where lymphocytes are produced in lymphopoiesis and mature (bone marrow & thymus gland)
• Produces B cells and T cells

Question 2

What are secondary lymphoid organs?

Answer 2

• Where lymphocytes can interact with antigens and with other lymphocytes
• Involves the spleen, lymph nodes and mucosal associated lymphoid tissues (MALT)

Question 3

What are other terms for the primary and secondary lymphoid organs?

Answer 3

Primary are generative lymphoid organs, secondary peripheral lymphoid organs

Question 4

Describe the structure of the thymus

Answer 4

• Medulla in the middle, cortex on the outside
• Located inbetween the lungs
• No obvious changes during infections

Question 5

What happens to thymic output with age?

Answer 5

Thymic output decreases

Question 6

Describe the structure of bone marrow in the foetus and in an adult.

Answer 6

• In the foetus present in all bones, liver and spleen. Marrow & cellular
• In adults mostly flat bones (vertebrae, iliac bones and ribs). Marrow & flat

Question 7

What is the function of red and yellow bone arrow? How is it laid out?

Answer 7

• Red produces blood cells
• Yellow consists of fat
• Red is around the outside. And yellow in the middle

Question 8

Describe the structure and function of a lymph node

Answer 8

Lymph node: drains fluid from between tissue cells

Question 9

Describe the structure and function of the spleen.

Answer 9

The spleen filters the blood for antigens.

Question 10

What is MALT?

Answer 10

Mucosa associated lymphoid tissue - small concentration of lymphoid tissues found in submucosal membrane sites.

Question 11

Describe the structure of gut associated lymphoid tissue

Answer 11

• The Peyers patch is mainly B cells, containing germinal centres during the immune response
• M cells in the mucosal epithelium communicate with the peyers patch.

Question 12

How does the body ensure that antigens meet the correct lymphocyte?

Answer 12

• Anatomical structure of the immune system

- Lymphocyte recirculation

Question 13

How does recirculation occur?

Answer 13

Naive lymphocytes travel through the blood to the peripheral lymphoid tissue where they are activated or they die.

Question 14

How do naive T cells enter the lymph nodes?

Answer 14

• T cells roll along the surface of the cells
• First bind to low affinity receptors, and then to high affinity receptors activated by chemokines
• Then undergo transendothelial migration

Question 15

List the cell types in the immune system

Answer 15

• B lymphocytes
• T lymphocytes
• Antigen Presenting Cells (dendritic cells, B lymphocytes, macrophages)

Question 16

How many different cell types in the immune system be differentiated?

Answer 16

Cluster of differentiation (CD markers) are used to discriminate between cells. They do have a function.

Question 17

What type of CD receptors do T lymphocytes have?

Answer 17

CD3. T helper cells (secrete cytokines) have CD4+, cytotoxic T cells (lyse infected cells) have CD8+.

Question 18

What type of antigens do T cells recognise?

Answer 18

Processed antigens in MHC (major histocompatability complex)

Question 19

How can B lymphocytes be identified?

Answer 19

• CD19 and CD20

- MHC class II (present antigens to helper T cells)

Question 20

What type of antigens are recognised by B cells?

Answer 20

• Intact free antigens in body fluids or on cell surfaces

- Use B cell receptors

Question 21

What are APCs?

Answer 21

• Antigen Presenting Cells
• Present processed antigen to T lymphocytes to initiate the adaptive immune response
• Include dendritic cells, B lymphocytes and macrophages