Cells of the Immune System

Question 1

Cells of the immune system: - - -

Answer 1

• circulate in the bloodstream - migrate into tissues to detect foreign antigens - accumulate in specialised organs where they develop and differentiate

Question 2

Name the types of white blood cells: - - - - -

Answer 2

• Monocytes - Eosinophils - basophils - Lymphocytes - Neutrophils

Question 3

Where do all WBC come from? What can they divide into?

Answer 3

They all originate from a pluripotent haemopoietic stem cell found in bone marrow They can divide to form: - common lymphoid precursors - megakaryocytes - granulocytes down the myeloid lineage - mast cells - monocytes in blood which may migrate to become macrophages

Question 4

What can common lymphoid precursors divide into? Where can all these lymphocytes migrate into?

Answer 4

Some migrate and emerge as B lymphocytes in the blood Others become NK cells in the blood Some go to the thymus and undergo differentiation and become T cells in the blood All these lymphocytes can migrate into the tissues and into secondary lymphoid tissues

Question 5

What will megakaryocytes give rise to?

Answer 5

Megakaryotes will give rise to platelets in the blood

Question 6

Where can macrophages arise from?

Answer 6

Further differentiation of monocytes from the blood, into the tissues Also from secondary lymphoid tissues

Question 7

What cells are involved in the secondary lymphoid tissues? What do these cells have in common?

Answer 7

Macrophages, interdigitating cells, dendritic cells All these cells are antigen presenting cells

Question 8

Briefly describe an antigen presenting cell

Answer 8

Very good at presenting antigen to other cells within the immune system

Question 9

What does the lymphoid lineage give rise to and its function?

Answer 9

Lymphocytes: involved in recognition and effector function

Question 10

What does the myeloid lineage consist of and the function of each cell type?

Answer 10

Granulocytes (short lived) - neutrophils - eosinophils - basophils all involved in effector cell function Monocytes: involved in recognition and effector functions, remove particulate matter

Question 11

Facts about neutrophils - - - - -

Answer 11

• constitute ~95% of circulating granulocytes - 10-20 microns in diameter - characteristic multi-lobed nucleus - predominant role: phagocytosis and destruction of pathogens - adhere to endothelial cells and enter tissues (diapedesis)

Question 12

What do neutrophils contain within their granules?

Answer 12

• lysosomes - acid hydrolases, myeloperoxidases, lysozyme and defensins Secondary granules - lactoferrin and lysozyme

Question 13

What type of nucleus does eosinophils have? What do they stain with?

Answer 13

• Characteristic bilobed nucleus - Cytoplasmic granules stain with eosin

Question 14

What does the crystalloid core of granules contain in eosinophils?

Answer 14

• Major basic protein = potent toxin for helminth worms - cationic protein - eosinophil derived neurotoxin

Question 15

What can eosinophils do to large pathogens?

Answer 15

They are able to bring about the killing of pathogens too large to be phagocytosed

Question 16

Basophils: - - -

Answer 16

• present in very small numbers in circulation - mast cells share characteristics with basophils but are only found in tissues - basophils have a segmented nucleus and large cytoplasmic granules

Question 17

What triggers both mast cells and basophils? What effect does this have?

Answer 17

• Allergens which trigger the allergic response to release contents of their granules

Question 18

Monocytes - -

Answer 18

• horse shoe shaped nucleus - many pinocytic vesicles and lysosomal granules

Question 19

What do lysosomes contain? Why is this important?

Answer 19

Lysosomes contain peroxidase and acid hydrolases - important for killing phagocytosed micro-organisms

Question 20

What is the major function of macrophages?

Answer 20

Disposal of microbes and dead body cells through phagocytosis

Question 21

Give examples of accessory cells and their functions: - - - -

Answer 21

• platelets: involved in blood clotting and inflammation - antigen presenting cells: present antigen to T cells - mast cells - endothelial cells: receptors recognise certain lymphocytes - control lymphocyte traffic and distribution

Question 22

What are the roles of monocytes, macrophages and antigen presenting cells in the immune response?

Answer 22

• phagocytosis, even clearing up dead neutrophils - concentrate antigen - process/present antigen to T cells - secrete growth factors, cytokines

Question 23

What do we need for a strong immune response?

Answer 23

• Cooperation between B cells, T cells and APC - cell to cell contact - secretion of cytokines

Question 24

What are lymphocytes required for?

Answer 24

Lymphocytes are involved in recognition and effector function

Question 25

What are the key roles of lymphocytes?

Answer 25

• Both cellular and humoral immunity - circulate all around the body - found in blood, lymph and specialised tissues - some are long lived e.g. memory cells

Question 26

Removal of lymphocytes results in: - -

Answer 26

• Inability to produce antibody - Inability to carry out cellular immunity

Question 27

What are the primary lymphoid organs: - -

Answer 27

• bone marrow - thymus

Question 28

Name some secondary lymphoid organs:

Answer 28

• spleen - lymph nodes - lymphoid nodules - waldeyer’s ring - bronchus associated lymphoid tissue - peyer’s patches - urogenital lymphoid tissue

Question 29

Where do common lymphoid precursors go?

Answer 29

• 25% in bone marrow and differentiate further to become B cells - 60% in thymus, into T cells - 15% result in natural killer cells

Question 30

What are cell markers?

Answer 30

• monoclonal antibodies are widely used to study cell surfaces - each mAb is highly specific for one antigenic determinant - Their use in experiments with immune cells has resulted in the development of a system of nomenclature: Cluster of Differentiation (CD) system

Question 31

What are all lymphocytes?

Answer 31

All lymphocytes are antigen specific - specific for only one antigenic determinant - has a specific antigen receptor on its surface

Question 32

Where is the specificity of lymphocytes acquired?

Answer 32

In the primary lymphoid organs: bone marrow and thymus

Question 33

How are B and T cells activated?

Answer 33

By encountering the particular antigen, specific for that lymphocyte

Question 34

What are B cells differentiated into? Cytotoxic T cells? Helper T cells?

Answer 34

B cells - plasma cells: factories for making immunoglobulin Tc cells - have granules containing proteins involved in killing Th cells - develop ability to produce growth factors or lymphokines

Question 35

What does binding of antigen to lymphocyte antigen receptor trigger?

Answer 35

Triggers clonal selection and expansion of specific lymphocyte for that antigen

Question 36

What is the key to adaptive immunity and why?

Answer 36

Clonal expansion which produces more activated and memory cells, therefore a more rapid, effective response