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General - Microbiology 🦠 > Immunology > Flashcards

Immunology Flashcards

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1
Q

What is immunology?

A

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

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2
Q

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

A

prevent or eradicate infections.

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3
Q

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

A

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)

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4
Q

What are the primary lymphoid organs?

A

BM

Thymus

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5
Q

What is bone marrow?

A
  • The BM is the site of B cell maturation.

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

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6
Q

What is the thymus?

A

Site of T cell maturation.

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7
Q

What are secondary lymphoid organs?

A
  • 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.
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8
Q

What is the function of secondary lymphoid organs?

A

Trap and concentrate antigens.

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9
Q

What are the cells of the immune system?

A
  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
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10
Q

What are immune cells that come from BM?

A

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

Phagocytes:-
• Macrophages
• Neutrophils

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

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11
Q

What is immune system discrimination?

A

self/non-self

Self-antigen ——> no immune response

Foreign antigen pathogen——-> immune response

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12
Q

How many layers does the immune system consist of?

A

3

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13
Q

What are the types of immunity?

A

The immune system has two lines of defense:

  1. Innate (non-specific) immunity.
  2. Adaptive (specific) immunity.
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14
Q

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

A

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

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15
Q

What are the characters of innate immunity?

A
  • 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
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16
Q

What are the components of innate immunity?

A
  • Barriers to infections
  • Innate immunity cells
  • Soluble defense
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17
Q

What are barriers to infection?

A

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.

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18
Q

What are innate immunity cells?

A

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

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19
Q

What are examples of soluble defense?

A
  • The complement system.
  • Cytokines of innate immunity.
  • Other plasma proteins of innate immunity:
    ▪ Mannose-binding lectin (MBL). ▪ C-reactive protein (CRP)
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20
Q

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

A
  • The circulating levels of these plasma proteins increase rapidly after infection.
  • This protective response is called “acute phase response”.
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21
Q

What are the characters of adaptive immunity?

A
  • 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
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22
Q

Specificity of the adaptive immunity

A

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

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23
Q

memory of the adaptive immunity

A

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

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24
Q

What is the function of B lymphocytes?

A

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

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25
Q

What is the function of T lymphocytes?

A

eradicate intracellular microbes (Cell-mediated immunity).

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26
Q

What is another function for B and T lymphocytes?

A

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

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27
Q

What are the types of adaptive immunity?

A

Humoral (antibody-mediated)
• B lymphocytes

Cell-mediated
• T lymphocytes

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28
Q

What are the sequences of adaptive immune response?

A
  • 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).
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29
Q

What are the cells activated in innate immunity?

A

Phagocytes: macrophages & neutrophils and NK cells

30
Q

What are the cells activated in adaptive immunity?

A

B lymphocytes T lymphocytes

31
Q

What are the receptors in innate immunity?

A

Pattern recognition receptors

32
Q

What are the receptors in adaptive immunity?

A

B cell receptor; BCR

T cell receptor; TCR

33
Q

What is the complement activation in innate immunity?

A

Alternative & MBL pathways

34
Q

What is the complement activation in adaptive immunity?

A

Classical pathway

35
Q

What are the cytokines in innate immunity?

A

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

36
Q

What are the cytokines in adaptive immunity?

A

IL-2, IL-4, IL-5, IFN-γ, IL-13, IL-17

37
Q

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

A

Naive —-> activated ——> effector

38
Q

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

A
  • Morphologically similar

* heterogeneous in phenotypes and functions

39
Q

What can the lymphocytes be distinguished with?

A

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

40
Q

What are the characters of B lymphocytes?

A
  • 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
41
Q

What is the function of B lymphocytes?

A

humoral immunity (antibodies)

42
Q

How do B lymphocytes recognize antigens?

A

by B cell receptor (BCR)

43
Q

What are B lymphocytes stimulated with?

A 
Stimulated by antigen leading to their proliferation & differentiation into
effector cells (plasma cells) that secrete antibodies and memory B cells.
44
Q

What do B lymphocytes destroy?

A

Microbes

45
Q

What are the characters of T lymphocytes?

A
  • “T” refers to Thymus derived
  • Developed & mature in the thymus
  • The majority of blood lymphocytes 75%.
  • Phenotype markers: TCR, CD3, CD4, CD8.
46
Q

What is the function of T lymphocytes?

A

cell-mediated immunity.

47
Q

What are the types of T lymphocytes?

A

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

48
Q

What are the subtypes of T lymphocytes?

A
  1. Helper T cells (CD4+) TH:
  2. Help B lymphocytes to produce antibodies
  3. Help macrophage activation to destroy ingested microbes.
  4. Cytotoxic T cells (CD8+) TC:
  5. Kill virus-infected cells.
  6. Kill tumor cells.
  7. Graft cells ….. Rejection.
  8. Regulatory T cells (Treg)
49
Q

How do T lymphocytes recognize antigens?

A

 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.

50
Q

What is the function of the proteasome?

A

Degrade Proteins into Peptides.

51
Q

What are the characters of NK cells?

A
  • A third population of lymphocytes.
  • 10% of blood lymphocytes.
  • Cytoplasmic granules
  • Phenotype markers: CD16
  • Antigen receptor: KARs and KIRs.
52
Q

What is the function of NK cells?

A

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

53
Q

KIRs

A
  • Killer inhibitory receptors

* (-) signal

54
Q

KARs.

A
  • Killer activating receptors

* (+) signal

55
Q

What is ADCC?

A

(Antibody-Dependent Cell-Mediated Cytotoxicity )

56
Q

What are phagocytes?

A

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

57
Q

What are the types of phagocytes?

A
  1. Monocytes/Macrophages

2. Neutrophils

58
Q

What are the characters of monocytes/macrophages?

A
  1. Monocytes circulate in blood … ingest microbes in blood
  2. Macrophages tissue-resident of monocytes …. Ingest microbes in
    tissues
59
Q

What are the characters of neutrophils?

A
  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
60
Q

What are the steps of phagocytosis?

A

• 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
61
Q

What is step 1 in phagocytosis?

A

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

62
Q

What is step 2 in phagocytosis?

A

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

63
Q

What is step 3 in phagocytosis?

A

• 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

64
Q

What is step 4 in phagocytosis?

A

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

65
Q

What is step 5 in phagocytosis?

A

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

66
Q

What is step 6 in phagocytosis?

A

• Intracellular killing
o oxygen-independent: lysosomal granules, lactoferrin, low pH, and lysosomal enzymes.

o oxygen-dependent: toxic oxygen-derived products and toxic nitrogen oxides

67
Q

What are the characters of APCs?

A
  • 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
68
Q

What is the function of APCs?

A
  1. Capture and transport antigens to peripheral lymphoid tissues
  2. Process antigens into pieces (peptides)
  3. Present peptides to T lymphocytes
69
Q

What are stem cells?

A

Stem cells are undifferentiated (unspecialized) cells

70
Q

What are the unique properties of stem cells?

A

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

71
Q

What are the two types of stem cells?

A
  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).
72
Q

What is the medical importance of stem cells?

A

• 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.

General - Microbiology 🦠 (6 decks)

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