Immunology 💉

Question 1

What is immunology?

Answer 1

is the study of the immune system, including its responses to microbial pathogens and damaged tissues and its role in disease.

Question 2

What is the most important physiological function of the immune system?

Answer 2

prevent or eradicate infections.

Question 3

What is the immune system and what does it consist of?

Answer 3

The immune system is the body’s defense against infectious agents and other foreign substances (antigens) in its environment, It consists of a complex network of cells, tissues, and organs ……….. Immune response (immunity)

Question 4

What are the primary lymphoid organs?

Answer 4

BM

Thymus

Question 5

What is bone marrow?

Answer 5

• The BM is the site of B cell maturation.

* Also, the site of generation of all blood cells from a common stem cell (hematopoiesis).

Question 6

What is the thymus?

Answer 6

Site of T cell maturation.

Question 7

What are secondary lymphoid organs?

Answer 7

• Include the lymph nodes and the spleen.
• Mucosa-associated lymphoid tissues including tonsils in the nasopharynx and Peyer’s patches in the sub-mucosal surfaces of the small intestine; also act as secondary lymphoid aggregates.

Question 8

What is the function of secondary lymphoid organs?

Answer 8

Trap and concentrate antigens.

Question 9

What are the cells of the immune system?

Answer 9

1. A common lymphoid progenitor producing:
   a. T lymphocytes
   b. B lymphocytes
   c. Natural killer (NK) cells.
2. A common myeloid progenitor producing:
   a. Leukocytes:
   b. Erythrocytes.
   c. Platelets

Question 10

What are immune cells that come from BM?

Answer 10

Lymphocytes:-
• B lymphocytes
• T lymphocytes
• NK cells

Phagocytes:-
• Macrophages
• Neutrophils

Antigen-presenting cells:-
• Macrophages
• Dendritic cells
• B lymphocytes

Question 11

What is immune system discrimination?

Answer 11

self/non-self

Self-antigen ——> no immune response

Foreign antigen pathogen——-> immune response

Question 12

How many layers does the immune system consist of?

Answer 12

3

Question 13

What are the types of immunity?

Answer 13

The immune system has two lines of defense:

1. Innate (non-specific) immunity.
2. Adaptive (specific) immunity.

Question 14

What do the innate and acquired immune systems use to sense potential threats?

Answer 14

The innate and adaptive immune systems utilize cell-surface receptors to sense potential threats (microbes).

Question 15

What are the characters of innate immunity?

Answer 15

• the First line of defense against pathogens and give a rapid response.
• Nonspecific
• no memory.
• Always present in healthy individuals.
• recognize and react against microbes only……. PAMPs

Question 16

What are the components of innate immunity?

Answer 16

• Barriers to infections
• Innate immunity cells
• Soluble defense

Question 17

What are barriers to infection?

Answer 17

o Physical barriers: include the epidermis and mucous membranes.

o Chemical and environmental barriers:
▪ pH: the acidic pH of the skin, stomach, and vagina inhibits the growth of pathogens.
▪ Microcidal molecules: α- and β- defensins), lysozyme, RNases, and DNases that.

o Biological barriers (commensal microbes): are
microbes (like flora) that exist in a symbiotic relationship with the body. They colonize skin, GIT, upper respiratory, urogenital tracts, and eyes and inhibit the establishment of pathogenic microbes.

Question 18

What are innate immunity cells?

Answer 18

a. Phagocytic cells: are cells having the ability to phagocytose (recognize, ingest, and
kill) microbes and any foreign antigen (phagocytosis)
• Macrophages
• Neutrophils

b. Natural killer (NK) cells: function in killing tumor cells and virus-infected cells

Question 19

What are examples of soluble defense?

Answer 19

• The complement system.
• Cytokines of innate immunity.
• Other plasma proteins of innate immunity:
  ▪ Mannose-binding lectin (MBL). ▪ C-reactive protein (CRP)

Question 20

What happens to the circulating levels of plasma proteins after infection?

Answer 20

• The circulating levels of these plasma proteins increase rapidly after infection.
• This protective response is called “acute phase response”.

Question 21

What are the characters of adaptive immunity?

Answer 21

• Second line of defense.
• Develops as a response to infection.
• Specificity and memory are characteristic features of adaptive immunity
• Lymphocytes are the cells of adaptive immunity

Question 22

Specificity of the adaptive immunity

Answer 22

the immune response is specific for a certain antigen Specificity ensures that different antigens elicit specific responses.

Question 23

memory of the adaptive immunity

Answer 23

is the ability to “remember” and respond more strongly to repeated exposure to the same microbe.

Question 24

What is the function of B lymphocytes?

Answer 24

produce antibodies that neutralize and eliminate the extracellular microbes and toxins (Humoral immunity).

Question 25

What is the function of T lymphocytes?

Answer 25

eradicate intracellular microbes (Cell-mediated immunity).

Question 26

What is another function for B and T lymphocytes?

Answer 26

recognize antigen by antigen-specific receptors present on their surfaces.

Question 27

What are the types of adaptive immunity?

Answer 27

Humoral (antibody-mediated) • B lymphocytes Cell-mediated • T lymphocytes

Question 28

What are the sequences of adaptive immune response?

Answer 28

- Antigen recognition by lymphocytes receptors. - Activation of lymphocytes leads to proliferation & differentiation into effector cells (cells that carry the function) and memory cells. - Elimination of the microbes. - Decline and termination of the immune responses (homeostasis) once the pathogen is eliminated to avoid damaging host tissues. - Long-lived memory (memory cells).

Question 29

What are the cells activated in innate immunity?

Answer 29

Phagocytes: macrophages & neutrophils and NK cells

Question 30

What are the cells activated in adaptive immunity?

Answer 30

B lymphocytes T lymphocytes

Question 31

What are the receptors in innate immunity?

Answer 31

Pattern recognition receptors

Question 32

What are the receptors in adaptive immunity?

Answer 32

B cell receptor; BCR | T cell receptor; TCR

Question 33

What is the complement activation in innate immunity?

Answer 33

Alternative & MBL pathways

Question 34

What is the complement activation in adaptive immunity?

Answer 34

Classical pathway

Question 35

What are the cytokines in innate immunity?

Answer 35

TNF, IL-1, chemokines, IFN-α, IFN-β, IFN-γ, IL-12

Question 36

What are the cytokines in adaptive immunity?

Answer 36

IL-2, IL-4, IL-5, IFN-γ, IL-13, IL-17

Question 37

What are the stages that a lymphocyte passes by to perform its function?

Answer 37

Naive —-> activated ——> effector

Question 38

What are lymphocytes similar in and what are they different in?

Answer 38

* Morphologically similar | * heterogeneous in phenotypes and functions

Question 39

What can the lymphocytes be distinguished with?

Answer 39

They can be distinguished by surface proteins the “CD” and a number

Question 40

What are the characters of B lymphocytes?

Answer 40

- Developed and mature in the BM. - B is derived from BM - 10-15% of total blood lymphocytes - Phenotype markers: o Antigen receptor (BCR) o CD19, CD21, o Recognize any antigen e.g. proteins, polysaccharides, lipids, nucleic acids

Question 41

What is the function of B lymphocytes?

Answer 41

humoral immunity (antibodies)

Question 42

How do B lymphocytes recognize antigens?

Answer 42

by B cell receptor (BCR)

Question 43

What are B lymphocytes stimulated with?

Answer 43

``` Stimulated by antigen leading to their proliferation & differentiation into effector cells (plasma cells) that secrete antibodies and memory B cells. ```

Question 44

What do B lymphocytes destroy?

Answer 44

Microbes

Question 45

What are the characters of T lymphocytes?

Answer 45

* “T” refers to Thymus derived * Developed & mature in the thymus * The majority of blood lymphocytes 75%. * Phenotype markers: TCR, CD3, CD4, CD8.

Question 46

What is the function of T lymphocytes?

Answer 46

cell-mediated immunity.

Question 47

What are the types of T lymphocytes?

Answer 47

CD4 OR CD8 o Helper T cells TH (CD4+) o Cytotoxic T cells TC (CD8+)

Question 48

What are the subtypes of T lymphocytes?

Answer 48

1. Helper T cells (CD4+) TH: 1. Help B lymphocytes to produce antibodies 2. Help macrophage activation to destroy ingested microbes. 2. Cytotoxic T cells (CD8+) TC: 1. Kill virus-infected cells. 2. Kill tumor cells. 3. Graft cells ..... Rejection. 3. Regulatory T cells (Treg)

Question 49

How do T lymphocytes recognize antigens?

Answer 49

 Recognize antigen by TCRs  Recognize protein antigens only.  They recognize antigen only in the form of peptide fragments plus MHC molecules on the surface of APCs (MHC Restriction): — CD4+ cells recognize peptide + class II MHC molecules. — CD8+ cells recognize peptide + class I MHC molecules.

Question 50

What is the function of the proteasome?

Answer 50

Degrade Proteins into Peptides.

Question 51

What are the characters of NK cells?

Answer 51

* A third population of lymphocytes. * 10% of blood lymphocytes. * Cytoplasmic granules * Phenotype markers: CD16 * Antigen receptor: KARs and KIRs.

Question 52

What is the function of NK cells?

Answer 52

— Killing tumor cells. — Killing virus-infected cells. — Antibody-dependent cellular cytotoxicity (ADCC) — Produce IFN-γ which activates macrophages.

Question 53

KIRs

Answer 53

* Killer inhibitory receptors | * (-) signal

Question 54

KARs.

Answer 54

* Killer activating receptors | * (+) signal

Question 55

What is ADCC?

Answer 55

(Antibody-Dependent Cell-Mediated Cytotoxicity )

Question 56

What are phagocytes?

Answer 56

Phagocytes are cells having the ability to phagocytose (recognize, ingest, and kill) microbes and any foreign antigen.

Question 57

What are the types of phagocytes?

Answer 57

1. Monocytes/Macrophages | 2. Neutrophils

Question 58

What are the characters of monocytes/macrophages?

Answer 58

1. Monocytes circulate in blood ... ingest microbes in blood 2. Macrophages tissue-resident of monocytes .... Ingest microbes in tissues

Question 59

What are the characters of neutrophils?

Answer 59

1. Polymorphonuclear leukocytes PMNs 2. The most numerous leukocytes in the blood 3. Increase in No. in blood ...acute infection 4. Ingest microbes and then die .. Pus cells

Question 60

What are the steps of phagocytosis?

Answer 60

• Delivery of phagocytes to the site of infection: o Diapedisis o Chemotaxis * Recognition of microbes * Phagocytic adherence to the target (opsonization) • Ingestion or engulfment of the target particle ..... Phagosome formation * Phagolysosome formation * Intracellular killing

Question 61

What is step 1 in phagocytosis?

Answer 61

• Delivery of phagocytes to the site of infection: o Diapedisis o Chemotaxis

Question 62

What is step 2 in phagocytosis?

Answer 62

• Recognition of microbes: phagocytes recognize microbes in blood and tissues by surface receptors specific for microbes e.g. Toll-like receptors TLRs

Question 63

What is step 3 in phagocytosis?

Answer 63

• Phagocytic adherence to microbes. o Opsonization: coating of the microbe by opsonin {antibody or complement C3b, C4b} o Binding of the microbe to receptors on phagocytic cells

Question 64

What is step 4 in phagocytosis?

Answer 64

• Ingestion (engulfment) of microbe into the cytoplasm of the cell within a membrane vesicle................. phagosome

Question 65

What is step 5 in phagocytosis?

Answer 65

• Fusion of phagosome with lysosome of the cell .... Phagolysosome{digestive vesicle}

Question 66

What is step 6 in phagocytosis?

Answer 66

• Intracellular killing o oxygen-independent: lysosomal granules, lactoferrin, low pH, and lysosomal enzymes. o oxygen-dependent: toxic oxygen-derived products and toxic nitrogen oxides

Question 67

What are the characters of APCs?

Answer 67

* include dendritic cells, macrophages, and some B cells * Present in the epithelium of the skin, GIT, respiratory tract ..... Entry of microbes * Capture, transport, process protein antigens into peptides and present the peptides to T cells. * They are rich in Class II MHC molecules

Question 68

What is the function of APCs?

Answer 68

1. Capture and transport antigens to peripheral lymphoid tissues 2. Process antigens into pieces (peptides) 3. Present peptides to T lymphocytes

Question 69

What are stem cells?

Answer 69

Stem cells are undifferentiated (unspecialized) cells

Question 70

What are the unique properties of stem cells?

Answer 70

o Self-renewal: numerous cycles of cell division by mitosis o Potency = the capacity to differentiate into specialized cell types e.g. Muscle cell, Pancreatic beta-cell, Red blood cell, Nerve cell, Brain cell, Liver cell, .....etc

Question 71

What are the two types of stem cells?

Answer 71

1. Embryonic stem cells: isolated from the inner cell mass of blastocysts 2. Adult stem cells: that are found in adult tissues (skin, muscles, umbilical cord blood, brain, heart, and bone marrow).

Question 72

What is the medical importance of stem cells?

Answer 72

• Stem cell therapy ....... Cell-based therapy • Treating patients by transplanting specialized cells that have been grown from stem cells in the laboratory (stem cell culture). o Leukemia: Bone marrow transplants o Cardiovascular disease: repairing damaged heart cells after a heart attack. o Type1 diabetes mellitus: replacing damaged pancreatic beta cells with functional beta cells which can secrete insulin. o Spinal cord injuries: damaged neurons. o Alzheimer's disease: replacing the damaged brain cells. o Muscle damage.