Cells, Organs, and Cytokines

Question 1

What is the unique capability of Hematopoietic stem cells (HSCs)?

Answer 1

They can renew or differentiate into many types of blood cells

-> Differentiate into Erythrocytes
-> Differentiate into Leukocytes

Question 2

What are the two paths a leukocyte can differentiate into?

Answer 2

-Myeloid: Granulocytes, Megakaryocytes, Erythrocytes, Monocytes (Macrophages, dendritic cells)

-Lymphoid: T cell (develop in Thymus), B-cells (bone narrow)
Innate lymphoid cell (ILC)

Question 3

What are the functions of the red blood cells and Megakaryotes?

Answer 3

-Red blood cells: transfer oxygen and also immune compounds

-Megakaryocytes: bud off platelets, which are used primarily as clotting factor

Question 4

What is the function of the Granulocytes?

Answer 4

-Neutrophils: they move around and wait for signals -> First circulating cell to the infection site, harm pathogens, can also phagocytose

-Basophils/mast cells: inflammation/allergies
-Eosinophils: antiviral, antiparasite activity

Question 5

Why is the nucleus of Granulocytes broken up?

Answer 5

Because it can easier squeeze into slids to get to the site of infection

Question 6

What do Granulocytes contain?

Answer 6

Proteases, antimicrobial proteins, protease inhibitors, Histamines, Ribonuclease (antiviral), Cytokines, Chemokines

Question 7

What is the function of adhesins?

Answer 7

-They are on the surface of immune and tissue cells, mediating the migration of cells

-Their activation and degradation is regulated by cytokines

Question 8

In which cells will Monocytes differentiate?

Answer 8

Macrophages (tissue-specific) -> function to repair/remodel, destroy pathogens (phagocytosis), present antigens

Dendritic cells -> “ingesters” of antigens, followed by presentation to naïve T lymphocytes

Question 9

Which receptors are encoded by T Helper and T cytotoxic cells?

Answer 9

T-Helper cells encode CD4 receptors –> interact MHC-II

T-cytotoxic cells encode CD8 receptors –> interact MHC-I

Question 10

What is the Function of T-helper and cytotoxic cells?

Answer 10

CD4-Helper cells: direct the adaptive immune system through cytokines

CD8 T-cells: convert to cytotoxic T-cells upon activation

Question 11

How are B-cells different from plasma cells?

Answer 11

B-cells turn into plasma cells upon activation, they lose membrane-bound B-cell receptor and produce the soluble variant of the BCR (antibodies)
NO MHC involved

Question 12

What are the characteristics of Innate lymphoid cells (ILC) and NK-cells?

Answer 12

NK-cells: They are the cytotoxic T cells of the innate immune system but lack T-cell receptors
their function is to kill infected or sick cells, mediated through signals

ILC: they absorb cytokines and amplify them, to direct the immune response in the right direction

Question 13

What are the antigen-presenting cells?

Answer 13

Usually MHC-II: Macrophages, B-cells, Neutrophiles, dendritic cells

Question 14

Which cells express unique recombinant receptors

Answer 14

T-cells (Th and Tc), B-cells,

Question 15

What cells originate from lymphatic lineage?

Answer 15

T-cells, B-cells, dendritic cells

Question 16

Which cells contain toxic granules?

Answer 16

Granulocytes, Neutrophiles, cytotoxic T-cells, Mastcells

Question 17

Which cells secrete cytokines?
Which expresses MHC-I?

Answer 17

ALL
ALL express MHC-I besides red blood cells

Question 18

What are the primary and secondary lymph organs?

Answer 18

Primary: Bone marrow, Thymus
Secondary: Lymph nodes, Spleen, MALT/GALT

Question 19

How can stromal cells contribute to the development of immune cells?

Answer 19

-facilitate HSC proliferation, direct migration, and stimulate differentiation

-B-lymphocytes develop in contact with stromal cells of the bone marrow

Question 20

Where does the development of the T-cells occur?

Answer 20

-initially in the bone marrow but then in the thymus (cortex and medulla)

-Cortex - positive selection: Can you interact with MHC-I or MHC-II?
95% fail
-negative selection: Kill off the auto-immune T-cells

-Medulla: after development, they will wait in the secondary lymph organs upon activation

Question 21

What is the role of the spleen?

Answer 21

-The first line of defense against bloodborne pathogens

-> Redblood cells in the red pulp, and white blood cells in the white pulp
specialized macrophages and B-cells in the marginal zone

Question 22

What is the MALT/GALT?

Answer 22

a layer of defense against infection at mucosal and epithelial layers
MALT: Mucosa-associated lymphoid tissue

Question 23

Which immune cells are located in the GALT?

Answer 23

-Naive T and B-cells
-Macrophages and dendritic cells provide innate cell defense
-Microfold (M) cells pass Ag across GI epithelium to antigen-presenting cells
-CD8 intraepithelial lymphocytes (IELs)
-Tuft cells detect helminth infections
-Goblet cells (mucus) and Paneth cells secret barrier immunity

Question 24

What are the functions of the Interleuikin-1 cytokines and which molecules stimulate them? Secreted by which cells?

Answer 24

-They promote inflammation
-It is stimulated by viral, parasitic, or bacterial antigens
-Secreted by macrophages and dendritic cells

Question 25

What are their functions locally and systemically?

Answer 25

-Acts locally on capillary permeability and pulls leukocytes to infected tissues
-act systemically to signal the liver to produce acute phase proteins
(cytokines, complement)

• help to activate the adaptive immune response

Question 26

What are the functions of class-1 cytokines?

Answer 26

.they have diverse targets and functions
-made by some T lymphocytes, It increases the growth and activity of other T lymphocytes and B lymphocytes

-includes IL-2 and growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF)

Question 27

What are the functions of class-2 cytokines? (Interferons)

Answer 27

Typ 1 Interferon: IFN-α and IFN-ß by macrophages/dendritic cells
-> induce synthesis of ribonucleases and inhibit protein synthesis (antiviral)

Typ 2 Interferon: IFN-γ
-> Produced by activated T/NK cells, modulates adaptive immunity

Typ 3 Interferon: IFN-λ
->Secreted by dendritic cells -> UPREGULATING genes controlling viral replication and host cell proliferation

Question 28

What are the functions of TNF Cytokines?

Answer 28

TNF-α is proinflammatory (produced by macrophages and others)
TNF-β is produced by activated lymphocytes -> delivers signals to leukocytes and endothelial cells

Question 29

What are the characteristics of IL-17 cytokines?

Answer 29

-are proinflammatory, predominate feature of TH17 cells
-stimulate further cytokine production, link innate and
adaptive immunity

-Receptors on neutrophils, keratinocytes, and other
nonlymphoid cells
exist as homodimers, all are transmembrane proteins

Question 30

What are Chemokines?

Answer 30

-responsible for leukocyte migration -> received by chemokine receptors

Question 31

What type of receptors bind to chemokines?

Answer 31

-Chemokine receptors are an example of G-protein-coupled
receptors -> interaction with GTP/GDP binding G protein

Many receptors can bind to more than one chemokine; and
several chemokines are able to bind to more than one receptor

Question 32

In which way do Cytokines act on different cells?

Answer 32

Cytokines mediate the effector functions of the immune system

-Autocrine action: binding to its self
-Paracrine action: effect nearby cells
-Endocrine action: effect distal cells through blood stream

Question 33

Explain the way Cytokines can act on different cells!

Answer 33

-Pleiotropic: 1 cytokine having different effects depending on the cell it is acting
-Redundant: different cytokines with similar effect

-Synergy: combines two cytokine activities to be greater than additive effect
-Antagonistic: one cytokine’s effect by inhibited by another’s cytokine action
-Cascade: one cytokine causing a cell to produce another cytokine

Question 34

What are the common features of Ligand-Receptor Interactions?

Answer 34

Binding occurs via multiple noncovalent bonds -> making it concentration-dependent and flexible

polymeric receptors provide further specificity for cytokine
signaling

Question 35

What happens after cytokine binds to a receptor?

Answer 35

-clustering of receptors and activation of cytoplasmic signaling cascade

-often several intercellular pathways are simultaneously activated resulting in a number of transcriptional and physical responses, like chemotaxis