Immune cells

Question 1

Cells involved in the immune response

Answer 1

All types of leukocytes, endothelial cells, adipocytes and epithelial cells

Question 2

Differentiation of immune cells

Answer 2

Leukocytes differentiate from self-renewing stem cells in the bone marrow

They then become pluripotent stem cells, at which point they are ‘committed’

The process relies on hormones and growth factors such as cytokines and colony stimulating factors (CSF)

Question 3

Myeloid progenitor lineage

Answer 3

Myeloid progenitor cells contain cytoplasmic granules

They give rise to mast cells, erythrocytes, platelets, basophils, eosinophils, neutrophils, monocytes and dendritic cells

These cells have have a polymorphic nucleus and are important for the innate immune response

Question 4

Neutrophils

Answer 4

The most prominent granulocyte

10-20 microns
Lifespan 2-3 days

Granules contain a variety of enzymes to kill bacteria and stain neutral

Main function is as a phagocyte

Question 5

Eosinophils

Answer 5

Granules contain eosin basic protein and stain red

Main function is against helminths and worms, although they have been known to phagocytose

Kill parasitic worms grouping around the parasite and simultaneously releasing their granules

Have receptors for antibody

Question 6

Basophils

Answer 6

Only enter the tissues during inflammation

Granules contain basophilic proteins and stain blue

Main function is to promote inflammation by releasing chemicals such as histamine

Can be stimulated in the lab to phagocytose

Have receptors for antibody

Question 7

Mast cells

Answer 7

Only fully differentiate after leaving th bone marrow

Found in connective and mucosal tissues

Cytoplasmic granules contain histamine and are important in the allergic response

Have receptors for antibody

Question 8

Macrophages/monocytes

Answer 8

Exist as monocytes in the blood and macrophages in the tissue

Main function is as a phagocyte but they also carry out antigen presentation to T-cells

Macrophages survive much longer and are much larger

Can be identified by their expression of CD14 and CD15

Question 9

Macrophages in different tissues

Answer 9

Liver = Kupffer cells 
Connective tissue = Histiocytes 
Lung = alveolar macrophages
Kidney = mesangial cells 
Brain = microglial cells
Bone = osteoclasts

Question 10

Dendritic cells

Answer 10

Irregularly shaped with many protruding branches

Are able to arise from both lymphoid and myeloid progenitor lineages

Main function is antigen presentation

Question 11

Megakaryocytes

Answer 11

Give rise to platelets by cytoplasmic fragmentation

Are polyploidy

Question 12

Lymphoid progenitor lineage

Answer 12

Lymphoid progenitor cells do not have cytoplasmic granules but have a large nucleus and small cytoplasm

Give rise to innate lymphoid cells, natural killer T-cells, natural killer cells, T-lymphocytes and B-lymphocytes

Question 13

B-lymphocytes

Answer 13

Differentiate and remain in the bone marrow

Express CD19 and CD21

Bind whole antigens via the B-cell receptor

Can differentiate into plasma cells or memory cells

Question 14

T-lymphocytes

Answer 14

Differentiate in the bone marrow and migrate to the thymus

Express CD3 and either CD4 or CD8

Bind antigen fragments via MHC molecules

Question 15

Innate lymphoid cells

Answer 15

Have a large, granular cytoplasm and kill cancerous and virally infected cells

Are considered to be between the adaptive and innate immune responses

Question 16

Natural killer T-cells

Answer 16

Have a T-cell receptor and kill cells in a similar way to CD8 cytotoxic T-cells

Synthesise many growth factors and signalling molecules

Question 17

Natural killer cells

Answer 17

Do not have a T-cell receptor

Other cell surface receptors recognise self and non-self structures