2 - Immune cells and organs

Question 1

What are primary lymphoid organs?

Answer 1

Where lymphocytes are produced

bone marrow and thymus

Question 2

The production of lymphocytes is known as _____

Answer 2

LYMPHOPOIESIS

Question 3

What are secondary lymphoid organs?

Name the 3

Answer 3

where lymphocytes interact with antigens and other lymphocytes

spleen
lymph nodes
MALT (mucosal associated lymphoid tissue)

Question 4

Where is the thymus located?

Answer 4

below the thyroid gland

Question 5

What are Hassall’s corpuscles?

Answer 5

whirls of fibroblasts where regulatory T-lymphocytes develop

Question 6

Where is bone marrow found in the foetus and in adults?

Answer 6

foetus - in all bones (as well as the spleen and liver)

adults - at the end of long, flat bones

Question 7

What are the changes in the bone marrow during infection/an acute phase response?

Answer 7

increased white cell production (leukocytosis)

Question 8

What are the 2 types of bone marrow?

Answer 8

RED - produces blood cells

YELLOW - fat

Question 9

Describe the layout of a lymph node

Answer 9

• highly organised - there are T cell and B cell areas
• B cell areas tend to be on the periphery
• B lymphocytes aggregate into follicles

Question 10

Describe what changes occur inside lymph nodes during infection

Answer 10

• when there is an ongoing immune response (and there is B lymphocyte proliferation), germinal centers form
• so the lymph node swells

Question 11

How do lymphocytes enter the lymph nodes from the circulation?

Answer 11

• leave the circulation via high endothelial venules

- directed by gradient of chemokines

Question 12

What happens in those without a spleen?

Answer 12

people can survive without a spleen
BUT
they are more susceptible to infection by encapsulated bacteria, so should be vaccinated against these bacteria

Question 13

Where is there lymphoid tissue near the epithelium? Give 2 names

Answer 13

near sites of likely infection

MALT (mucosa associated lymphoid tissue) and the cutaneous immune system

Question 14

What is found in the Peyer’s patch?

Answer 14

contains germinal centers during immune response

predominantly B cells

Question 15

What are langerhans cells and where are they found?

Answer 15

dendritic cells of skin and mucosa

they capture antigens in their local environment and migrate via lymphatic vessels to the draining lymph nodes

Question 16

Why are Cluster of Differentiation markers used?

Answer 16

cannot differentiate between lymphocytes under a microscope

Certain clusters of antibodies recognise certain cell surface proteins

Question 17

What are the T-cell subsets?

Answer 17

CD4 - T-helper cells, regulatory T-cells - secrete cytokines

CD8 - cytotoxic T-cells - lyse infected cells and secrete cytokines

Question 18

How are antigens recognised by T-cells?

Answer 18

• T cells only recognise processed antigens
• recognised by the T-cell receptor
• antigens must be presented with an APC on their surface by a MHc molecule

Question 19

B-lymphocytes express which MHC class?

Answer 19

II

Question 20

What cell do they present antigens to?

Answer 20

Helper T-cells

Question 21

How are antigens recognised by B-cells?

Answer 21

• they recognise intact antigens
• recognised by a B-cell receptor
  NOTE: the BCR is a membrane anchored form of the antibody they they produce when activated

Question 22

What happens at the secondary lymphoid tissue?

Answer 22

antigens are presented by APCs

Question 23

List the 3 antigen presenting cells and where they are located

Answer 23

• dendritic cells - widely spread (skin and mucosal tissue)
  NOTE: there are also follicular dendritic cells that are located in the lymph node follicles (but these present to B-cells)
• B-lymphocytes - in lymphoid tissue
• Activated macrophages - in lymphoid tissue

NOTE: all these cells (except FDCs) present to T-cells via MHC

Question 24

What CD markers do ALL B-cells express?

Answer 24

CD19 and CD20