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Theme 2.1 Microbiology > Immunology (microbiology) > Flashcards

Immunology (microbiology) Flashcards

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1
Q

What is immunity

A

Resistance to disease, specifically infectious disease

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2
Q

What is the immune system?

A

The collection of cells, tissues, and molecules that mediate resistance to infections

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3
Q

What is the IMMUNE RESPONSE?

A

The coordinated reaction of these cells and molecules to infectious microbes.

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4
Q

What is IMMUNOLOGY?

A

The study of the immune system, including it’s responses to microbial pathogens and damaged tissues and its role in disease.

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5
Q

The most important physiological function of the immune system is to

A

PREVENT infections and to ERADICATE established infections.

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6
Q

Discuss the vaccination and the idea behind vaccination.

A

Conversely stimulating the immune response against microbes through vaccination is the most effective means of preventing infection.

VACCINATION- A process of induction of immunity to a pathogen by deliberate injection of a weakened , modified or related form of the pathogen which is no longer pathogenic

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7
Q

Many inflammatory diseases are caused by an

A

ABNORMAL immune response.

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8
Q

The immune response is the major barrier to successful —- to treat organ failure

A

organ transplantation

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9
Q

The importance of the immune system is illustrated by observation that individuals with defective immune responses are

A

susceptible to serious life threatening infections.

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10
Q

The immune system also prevents the growth of

A

some tumours.

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11
Q

The immune response also participates in the clearance of

A

dead cells and initiating tissue repair.

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12
Q

Diagnostics→ products of the immune cells e.g. antibodies are used in serological tests in order to

A

diagnose a variety of infections.

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13
Q

What is the role of the immune system?

A
  1. Defence against infections
    =Deficient immunity→increased susceptibility to infections
    Vaccination boosts immune defences and protects against infections
  2. Defence against tumours
    =Potential for immunotherapy of cancer
  3. The immune system responds to tissue grafts and newly introduced molecules
    =Immune responses are barriers to transplantation and gene therapy
  4. The immune system can injure cells →induce pathologic inflammation
    =Abnormal immune responses are the cause of allergic, autoimmune and other inflammatory diseases
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14
Q

The two types of immunity?

A

INNATE (NATURAL) IMMUNITY – Mediates the initial protection against infections

ADAPTIVE (ACQUIRED) IMMUNITY – Develops slowly and provides more specialised and effective defence against infections

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15
Q

Discuss the path taken by an infectious agent when it first gets into the body.

A

An infectious agent first encounters elements of the innate immune system. These may be sufficient to prevent disease. But if not , disease results.

The adaptive immune response is then activated to produce recovery. And specific immunologic memory. . Following re-infection with the same agent, no disease results. And the individual has acquired immunity to the infectious agent

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16
Q

INNATE (NATURAL) IMMUNITY

A

Always present in healthy individuals.
Consists of physical /chemical /biochemical properties
Biochemical – lysozyme(tears,nasal secretions, saliva), sebaceous gland secretions, commensal organisms in gut and vagina ,spermine (semen)
Physical /chemical – skin, mucus, cilia lining the trachea, acid in the stomach

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17
Q

First line of defence is provided by

A

epithelial barriers and by cells present in the epithelia

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18
Q

LIST THE FIRST LINES OF DEFENCE

A
  1. Saliva - antibacterial enzymes
  2. Skin - prevents entry
  3. Stomach acid - low pH and kills harmful microbes
  4. Tears - anibacterial enzymes
  5. Mucus linings- trap dirt and microbes
  6. “good” gut bacteria - out compete bad bacteria
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19
Q

What are the cells involved in INNATE IMMUNITY?

A

Cells / soluble factors

Phagocytes
Natural killer cells (specialised lymphocytes)
Dendritic cells
Complement
Acute phase proteins e.g. C - Reactive protein

When cells breach the barrier and enter tissues/circulation they are attacked by phagocytes and specialised lymphocytes called nk cells. In addition the innate immunity also enhances the adaptive immunity.

20
Q

ADAPTATIVE (ACQUIRED) IMMUNITY

A

This type of immunity has to ADAPT to the presence of microbial invaders.
Therefore requires expansion and differentiation of cells (lymphocytes) before it can provide an effective defence

21
Q

Two types of adaptive immunity

A
  1. Cell-Mediated Immunity (CMI)

2. Humoral immunity

22
Q
  1. HUMORAL IMMUNITY
A

Mediated by proteins called antibodies.
Antibodies are produced by cells called B lymphocytes.
Secreted into circulation, and mucosal fluids.

ROLE: Eliminate microbes and microbial toxins that are present OUTSIDE host cells i.e. they STOP microbes that are present at mucosal sites/blood from invading host cells and connective tissue

These antibodies cannot get gain access to organisms that live INSIDE infected cells (intra-cellular organisms)

Therefore defence against intracellular organisms requires another form of immunity i.e. Cell mediated immunity (CMI)

23
Q
  1. CELL-MEDIATED IMMUNITY
A

Mediated by cells called T-Lymphocytes
Different types of T-lymphocytes e.g. Helper-T-lymphocytes, cytotoxic T- lymphocytes

ROLE:
Eliminate intracellular microbes
Kill infected cells
Eliminate reservoirs of infection

24
Q

What are the features of adaptive immunity?

A
  1. Specificity
    =Ensures distinct responses for specific microbial molecule (antigens)
  2. Diversity
    =Enables the immune system to respond to a large variety of antigens
  3. Memory
    =Enables rapid and enhanced responses to repeated exposures to the same antigen
  4. Non-reactivity to self
    =Prevents injury to host during the response to foreign microbes
25
Q

What is Passive immunity?

A

Only physiological example – NEWBORNS

Their immune systems are not mature enough to respond to many pathogens

They acquire antibodies from their mothers via the placenta and breast milk thereby facilitating protection against infections.

26
Q

3 broad groups of cells in the immune system

A

Lymphocytes

Antigen-presenting Cells

Effector Cells

27
Q

Antigen -presenting cells

  • overall function
  • Different types and their specific functions
A

Overall function: Capture antigens and display them to lymphocytes

  1. Dendritic cells
    =Capture antigens and transport them to lymph nodes → here they display the antigens to T lymphocytes
  2. Macropahges
    = Phagocytosis of microbes in tissues
  3. Follicular dendritic cells
    =Reside in peripheral lymphoid organs and present antigens to B cells.

**B lymphocytes also act as antigen-presenting cells.

28
Q

Effector cells

A

Overal function: Eliminate antigens

  1. T lymphocytes
  2. Macrophages /monocytes
  3. Granulocytes: neutrophils/eosinophils
29
Q

Lymphycytes

  • Overall function
  • Different types and their specific functions
A

Overall function: Specific recognition of antigens (microbial molecules)

  1. B lymphocytes
    =Mediators of humoral immunity.
    Neutralize the microbe, Activate complement and Phagocytosis
  2. T Lymphocytes

i)Helper T =Mediators of cell-mediated immunity
Activate macrophages ,
Inflammation
Further activation of B/T Lymphocytes
ii) Cytotoxic T (CTL) = Direct killing of infected cell
iii) Regulatory T = Suppression of the immune response

  1. Natural killer cells
    =Cells from innate immune system
    Directly kills infected cells
30
Q
  1. T Lymphocytes
A

i)Helper T =Mediators of cell-mediated immunity
Activate macrophages ,
Inflammation
Further activation of B/T Lymphocytes
ii) Cytotoxic T (CTL) = Direct killing of infected cell
iii) Regulatory T = Suppression of the immune response

31
Q

Tissues of the immune system

A
  1. Generative lymphoid organs
  2. Peripheral lymphoid organs
    3.
32
Q

1)GENERATIVE LYMPHOID ORGANS

A 
Bone marrow ( B lymphocytes)
Thymus (T lymphocytes)

Here the B and T lymphocytes are allowed to mature and become competent to respond to antigens

33
Q

2) PERIPHERAL LYMPHOID ORGANS

A

Consists of lymph nodes, the spleen ,mucosal and cutaneous immune systems.

Here , adaptive immune responses are initiated

34
Q

Discuss lymph nodes

A

They are encapsulated nodular aggregates of lymphoid tissue
Located throughout the body

*Lymph is a fluid that is constantly leaking out of all blood vessels in all epithelia, CT, and most parenchymal organs. This lymph is drained by lymphatic vessels from the tissues to the lymph nodes

35
Q

Discuss the spleen

A

Highly vascular abdominal organ

Responsible for eliminating blood borne antigens

The spleen contains abundant phagocytes which ingest and destroy microbes in the blood.

36
Q

Cutaneous immune system and mucosal immune system

A

Cutaneous immune system
=Collection of lymphoid tissues under the epithelia of skin

Mucosal Immune system
=Collection of lymphoid tissue in the gastrointestinal tracts (Peyer’s patches) and respiratory tracts

37
Q

Overview of immune responses to Microbes – sequence of events.

From when the microbe enter the system

A

**Microbe enters

  1. Early immune response
  2. Adaptive immune response
  3. Decline of immune response and memory
38
Q

Principle barriers between host & environment →

A
  1. epithelia(skin),
  2. GI and
  3. respiratory tracts.

These barriers impede entry of microbes

**Innate immunity can eradicate some infections and keep other pathogens in check until the more powerful adaptive immune response is activated

39
Q

EARLY IMMUNE RESPONSE

A

If the microbe traverses the epithelia , they encounter other components of the innate immunity

These include phagocytes (which include neutrophils/macrophages ) → ingest microbes into vesicles and destroy them by producing microbial substances.

Macrophages and dendritic cells also secrete CYTOKINES → results in INFLAMMATION ( brings leucocytes and other proteins to the site of injury)

Important to note that the innate immune system also provides signals that initiate the adaptive immune system

40
Q

The adaptive immune response has distinct immune phases :

A

a) antigen recognition and capture
b) lymphocyte activation
c) antigen elimination
d) homeostasis and memory

41
Q

a) antigen recognition and capture

A

Microbes (antigens) that enter the epithelia are captured by dendritic cells (reside in epithelia)

They are then transported to draining lymph nodes

Inside the dendritic cells the antigens are processed (broken down) into smaller pieces (peptides)

The dendritic cells then display the peptides on the surface of the cell → giving rise to the term ANTIGEN PRESENTING CELL (APC)

These peptides are then recognized by B and T lymphocytes → initiation of T cell responses (proliferation and differentiation)

42
Q

b) lymphocyte activation + c) antigen elimination

A

When naïve t lymphocytes are activated by peptides → secrete cytokines (act as growth factors) → results in proliferation and differentiation into effector cells

These effector T- cells (generated in lymphoid organs) migrate back into the circulation to the site where the initial microbe (antigen) entered.

Here the T lymphocytes serve in various ways to eliminate the organism

43
Q

How are B lymphocytes also Antigen-presenting cells?

A

B lymphocytes → also differentiate and proliferate in to plasma cells

Plasma cells secrete different classes of antibodies which have distinct functions
B lymphocytes also ingest the antigens and break them down into peptides → display them on their surface for T lymphocytes to recognize → hence they are also ANTIGEN PRESENTING CELLS

**Hereby further activating the T cell responses

44
Q

Discuss how antibodies work

A

Antibodies bind to microbes and prevent them from infecting cells

Antibodies also coat the microbes (opsonize) the microbes and make them targets for phagocytes (macrophages and neutrophils)

Antibodies activate complement → Phagocytosis and the destruction of microbes are enhanced

45
Q

d) Homeostasis and Memory

A

After elimination of the organism majority of the lymphocytes die by apoptosis

Thereby returning the immune system to a basal resting state (homeostasis)

The initial activation of T lymphocytes generates long-lived memory cells → that survive for years after infection and they mount rapid and robust responses upon encounter with the same antigen

46
Q

IMMUNITY SUMMARY FLASHCARD

A
  1. pathogen recognition and initial attack
    cells involved are macrophages, neutrophils, natural killer cells, and antigen-presenting cells
  2. Transmission of pathogen information to the adaptive immune system via dendritic cells. Moving to lymph nodes.

Gets there gives the presented microbe to T-cells and activates them. The activated t-cell interacts with B-cell and activates the b-cell.

From activated t-cell, we get cytotoxic t-cells and from activated b-cell, we get Plasma cells and –> antibodies and some memory cells.

All lead to:

  1. Specific attack on pathogens

Theme 2.1 Microbiology (10 decks)

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