Defence Cells

Question 1

What are cells of myeloid (innate) origin?

Answer 1

neutrophils, macrophages, monocytes, eosinophils, basophils, mast cells

Question 2

What is myeloid?

Answer 2

Having to do with or resembling the bone marrow.

Question 3

What is lymphoid?

Answer 3

originate from precursor cells in the bone marrow, but they mature in the lymphoid organs, such as the thymus and lymph nodes.

Question 4

What are cells of myeloid or lymphoid (innate) origin?

Answer 4

dendritic cells,

Question 5

What are cells of lymphoid (adaptive) origin?

Answer 5

T cells
B cells

Question 6

Where do nearly all innate and adaptive cells originate from?

Answer 6

bone marrow

Question 7

5 years after periodontal treatment, what % of patients regress to pre-treatment periodontitis?

Answer 7

45%

Question 8

What does build up of dental plaque cause?

Answer 8

microbial dysbiosis

Question 9

Does removal of plaque lead to resolution?

Answer 9

not always

Question 10

What are the precursors of macrophages?

Answer 10

monocytes

Question 11

What do monocytes differentiate into?

Answer 11

macrophages

Question 12

What is the location and characteristics of monocytes/macrophages?

Answer 12

stored in spleen, migrates through blood
early responders to infection or tissue damage
long-lived with multiple functions
phagocytose and present antigen

Question 13

What type of cell are mast cells?

Answer 13

granulocytes

Question 14

What are the characteristics of mast cells?

Answer 14

early responders to infection or tissue damage
migrate from blood and differentiate in tissues (blood precursors not well defined)
protect against pathogens (particularly parasitic worms)
best known for role in allergy (release histamine)

Question 15

What can loss of mast cells in the gingivae lead to?

Answer 15

enhanced PD progression

Question 16

What type of cells are neutrophils?

Answer 16

granulocytes

Question 17

What are characteristics of neutrophils?

Answer 17

Phagocytic granulocytes
Most numerous/important cells in innate immune responses
Circulate in blood and move into tissue when required
Contain numerous granules (intracellular vesicles)
Have NETS (neutrophils extracellular traps)

Question 18

Where are neutrophils found in the oral cavity?

Answer 18

neutrophils are mainly found in the junctional epithelium and in the gingival crevicular fluids

Question 19

What are characteristics of basophils and eosinophils?

Answer 19

Granulocytes
Less abundant than neutrophils
Contain granules – degradative enzymes and antimicrobials
Eosinophils play a major role in defence against parasites as larger than neutrophils so can ingest larger threats
Both also contribute to allergy (basophils produce histamine)

Question 20

What is the main aim of dendritic cells?

Answer 20

to orchestrate the adaptive immune response – induce immune memory for adaptive immune cells (B cells/ T cells) to recognise microbial antigens

Question 21

What is the linage of dendritic cells?

Answer 21

myeloid and lymphoid lineage

Question 22

What are the functions of dendritic cells?

Answer 22

Degrade pathogens but major function is not clearance but to present antigen (antigen presenting cell [APC]) to T cells (sometimes directly to B cells)

Question 23

Describe memory generation in DCs

Answer 23

Immature dendritic cells take up and process antigen in the epidermis
Once taken up antigen they migrate to lymph nodes and differentiate along the way
Mature dendritic cells have co-stimulatory activity and can prime naïve T cells
They can also transfer antigen to other dendritic cells resident in the lymph node

Question 24

What are the characteristics of NK cells?

Answer 24

Considered part of innate immunity (unlike other lymphoid cells)
Large cells with granules
Recognize and kill abnormal cells/tumours/viral infected cells via cytotoxic lytic granules
Important for ‘holding back’ virus infections until adaptive immunity kicks in

Question 25

What are the characteristics of innate lymphoid cells (ILCs)?

Answer 25

Non-cytotoxic members of NK cell family Innate immune cell of lymphoid origin (not myeloid) Link innate and adaptive immune immunity Three main subsets (ILC1s, ILC2s and ILC3s) Produce effectors (cytokines) similar to T cell subsets

Question 26

Where do T cells mature?

Answer 26

thymus

Question 27

What is the main function of T cells?

Answer 27

cellular immunity

Question 28

How do T cells recognise peptides?

Answer 28

Recognize peptides presented by APCs through the T Cell Receptor (TCR)

Question 29

Where are T cells found mostly?

Answer 29

lymphoid organs

Question 30

T cells can respond to numerous antigens, what is this called?

Answer 30

T cell repertoire

Question 31

What prevents T cells recognising self peptides?

Answer 31

Checkpoints in place in Thymus (Thymic education) to prevent T cells responding to themselves

Question 32

What do the 3 T cell types start off as?

Answer 32

All T cells start as a naïve cell and have receptor for very specific proteins (e.g., antigens via DC presentation)

Question 33

What are the 3 T cell types and what is their function?

Answer 33

T helper cells (CD4+) function to help support other cells by secreting cytokines and activating B cells Cytotoxic T cells (CD8+) destroy our own cells which have become infected (usually virus-related) Regulatory T cells (Tregs) regulate or suppress other cells in the immune system

Question 34

What enzymes do CD8+ cells produce?

Answer 34

perforins granzymes

Question 35

What are the subsets of CD4+ cells and what do they do?

Answer 35

TH1 – support macrophage to destroy microbes TH2 – allergic responses/plasma cell generation (IgE), produce cytokines which recruit and activate mast cells, eosinophils TH17 – fungi/ extracellular bacteria secrete IL-17, IL-22 cytokines that promotes release of cytokines and chemokines from non professional Immune cells (epithelial cells) TFH – found predominantly in lymph nodes and important for B cell antibody generation Tregs – control/dampen the immune response

Question 36

What do B cells produce?

Answer 36

antibodies

Question 37

What are the two main types of B cells?

Answer 37

memory and plasma

Question 38

What leads to a generation of two subsets of B cells?

Answer 38

clonal expansion

Question 39

What is the function of plasma B cells?

Answer 39

antibody factory

Question 40

What is the function of memory B cells?

Answer 40

set out a quicker antibody reaction to infections

Question 41

Apart from the two main types of B cells, what else can B cells do?

Answer 41

B cells also have the potential to take up and present antigen – leading to T cell activation

Question 42

What are cells of myeloid or lymphoid (innate) cells?

Answer 42

dendritic, NK C, ILCs

Question 43

How do dendritic cells attach to antigens?

Answer 43

Toll like receptors

Question 44

What are the 3 signals required for naive T cell determination?

Answer 44

1’ MHC-TCR interaction 2’ co-stimulatory molecules interactions (CD80/CD86 and CD40 on Dendritic cells C ---- CD40L and CD28 on T cell) 3’ signal dictates what T helper cell the naïve cell becomes. mediated by cytokine (IL2)

Question 45

What molecules do B cells also have?

Answer 45

they also have the same co-stimulatory molecules that professional antigen presenting cells have