Cells of the Immune System

Question 1

What are the 2 lineages of immune cell?

Answer 1

Lymphoid and myeloid

Question 2

What are the 3 interacting barriers of the immune system?

Answer 2

1. Epithelial & Mucosal surfaces
2. Innate immune system (general inflammation response)
3. Adaptive immune response to specific threat

Question 3

What are the functions of epithelial cells?

Answer 3

• Block entry to microorganisms
• Produce antimicrobial proteins which kill most pathogens
• Produce regulatory proteins (cytokines & chemokines) and mucins

Question 4

What are goblet/paneth cells?

Answer 4

Specialised cells found in endo and epithelial mucosal surfaces often exposed to infection
Contain crypts which secrete mucous and antimicrobial proteins

Question 5

Describe the properties of neutrophils

Answer 5

• Small granulated cells with a lobate nucleus
• Have cytoplasm neutral staining
• 50-70% of blood leucocytes and have a short lifespan (5 days)

Question 6

What is the function of neutrophils?

Answer 6

• Phagocytic, provide key role in inflammatory response

- Granules contain elastase and antimicrobial proteins (for intracellular killing of bacteria)

Question 7

Describe the properties of eosinophils

Answer 7

• Slightly bigger than neutrophils with acidic staining
• 1-6% of blood leucocytes
• In blood for a few hours but in tissues for a few weeks

Question 8

What is the function of eosinophils?

Answer 8

• Inflammatory response to parasites, allergic reactions and asthma
• Present antigen to T cells
• Granules release peroxidase, anti-parasite toxins, collagenase as extracellular effectors

Question 9

Describe the properties of basophils

Answer 9

• Bilobate nucleus with granular basophilic cytoplasm
• Rarest of blood leucocyte types
• Life span of 70 hours

Question 10

What are the functions of basophils?

Answer 10

• Granules release histamine, heparin, cytokines, serotonin & chondroitin
• Involved in inflammation & allergic reactions via IgE binding

Question 11

Describe the properties of monocytes

Answer 11

• Large cells making up 3-8% of blood leucocytes
• Subsets distinguished by surface receptors
• Migrate to reservoirs in tissues (e.g spleen) where they mature to other leucocyte types

Question 12

What are the functions of monocytes?

Answer 12

• Present antigens and produce signalling molecules

- Clear out debris via phagocytosis

Question 13

What is the function of platelets/thrombocytes?

Answer 13

• Involved in clotting
• Express MHC I and possess receptors for IgG
• Release chemotactic factors

Question 14

What are lymphocytes?

Answer 14

Small, round, non-phagocytic cells which are the made enactors of adaptive immunity

Question 15

What are the 2 types of lymphocytes?

Answer 15

T-cells - mature in thymus and kill infected/cancer cells via antibodies (CD40)
B-cells - made in bone marrow and also secrete and synthesise antibodies (CD4 and CD8)

Question 16

What are the 3 types of T cell? What are their markers?

Answer 16

T-helper - release cytokines, recognise antigens and activate T-killer cells and B-cells, CD4+ marker
T cytotoxic - Kill virus infected, cancerous, foreign and damaged cells. Has CD8+ marker
T regulatory - Modulates immunity and maintains self-tolerance, identified by CD4+ and CD25+ markers

Question 17

What are natural killer (NK) cells?

Answer 17

• Small granules containing perforin and granzymes
• Kill cells without antibodies
• Produce cytokines

Question 18

What is the role of macrophages?

Answer 18

• Found in tissues and derived from monocytes
• Large cells consume bacteria, debris and dead cells
• Also aid in adaptive response via antigen presentation

Question 19

Describe dendritic cells?

Answer 19

• Small stellate cells derived from the bone marrow
• Sample blood for pathogens (common in tissues with external contact)
• When activated, interact with B and T cells in the lymph nodes in order to initiate an adaptive immune response

Question 20

What is the function of mast cells?

Answer 20

• Highly granulated cells rich in histamine and heparin
• Present in connective tissue/mucosa
• Degranulation occurs upon injury or after binding to IgE or complement

Question 21

Which lineage evolved first?

Answer 21

Myeloid (innate)

Question 22

Where is the thymus found?

Answer 22

Between the lungs

Question 23

Describe the maturation process of a T-cell

Answer 23

1. T-cell precursors travel from the bone marrow to develop in the thymus, then are ‘selected’
2. Mature T-cells leave the thymus and travel to the secondary lymphoid tissues (spleen, lymph node, GALT)

Question 24

Describe the structure of the thymus

Answer 24

• Consists of lobules with outer cortex and inner medulla
• Cortex contains immature T-cells
• Medulla contains mature T-cells

Question 25

Where are B cells found in the lymph nodes?

Answer 25

• In follicles where they undergo proliferation after activation
  (note: T-cells found in areas around follicles)

Question 26

What is the structure and function of the spleen?

Answer 26

• White pulp contains lymphocytes
• Red pulp contains blood sinuses & macrophages
• Role is to collect and destroy old red blood cells, filtering the blood and traping microorganisms