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PBS 602 Pathophysiology > Innate and Adaptive Immunity > Flashcards

Innate and Adaptive Immunity Flashcards

1
Q

the nature of the immune system

A
  • the resistance and defense against diseases particularly infectious diseases.
  • The collection of cells, tissues, and molecules that allow the body to resist diseases is called the immune system
  • reaction to the infectious agent is what we call the immune response
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2
Q

The main function of the immune system is

A

eradicate infections

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3
Q

Obligate pathogen

A

Any organism that causes disease such as bacteria, viruses, fungi, and parasites.

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4
Q

Opportunistic pathogens

A

organisms that cause diseases in immunocompromised individuals or if they gain access to sites in the body where they are not normally located.

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5
Q

Commensal organisms

A

they are found in healthy humans or animals and do not cause diseases under normal conditions

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6
Q

Microbiota

A

Normal flora in different parts of the body such as the skin, oral cavity, gut, and urogenital tract. They usually cause no harm and may provide benefit.

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7
Q

Primary lymphoid organs

A

where immune cells are produced and mature

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8
Q

Secondary lymphoid organs:

A

where the immune responses occur e.g. lymph nodes, spleen, and tonsil

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9
Q

The immune cells

A

represent the key players of the immune system and are derived from hematopoietic stem cells in the bone marrow

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10
Q

common lymphoid progenitor

A
  • lymphocytes (T or B cells)
  • B cells give rise to plasma cell
  • NK cell
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11
Q

common myeloid progenitor

A

myeloid cells (monocytes⇒ macrophages , dendritic cells; and granulocytes ⇒ i.e. neutrophils, eosinophils, and basophils)

Mast cells

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12
Q

innate immunity

A
  • non specific
  • rapid
  • does not change upon repeated exposure
  • no memory
  • not affected by immunization or prior contacts
  • resistance from genetic and constitutional make up
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13
Q

Adaptive Immnuity

A
  • Second line of defense
  • Specific
  • Slow
  • Has memory and can improve upon repeated exposure to the same pathogen
  • Activated by immunization or prior contacts ( flu shot)
  • Resistance acquired upon exposure to infections agents
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14
Q

Complement System

A
  • complement proteins are proteolytic enzymes
  • All of the pathways lead to the production of C3b. C3b then initiates the late steps of complement activation leading to the final production of membrane attack complex (MAC) which is a transmembrane channel, composed of polymerized C9 molecules, that lyses the microbes.
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15
Q

What is an Opsonin?

A
  • Any protein that coats the microorganism facilitating its phagocytosis by phagocytes such as macrophages and neutrophils.
  • C3b and C4b are opsonins and they have receptors on phagocytes.
  • Antibodies such as IgG can serve as opsonins.
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16
Q

Innate immune reactions

A

functions mainly through the induction of inflammatory responses and antiviral defense mechanisms.

The nature of the innate immune reaction is dependent on the type of the microbe.

17
Q

The major protective innate immune responses are:

A

1- Acute inflammatory response (inflammation) mediated by complement system, neutrophils and monocytes recruited to the site of infection.

2- Phagocytic elimination of pathogens

3- Antiviral innate immune reactions through type I interferons and natural killer cells.

18
Q

1- Inflammatory immune response

A
  • a type of tissue reaction that provides immediate response to invading pathogens and is mediated by innate immune cells and proteins (complement system)
  • main goal is to eliminate pathogen at site of infection and prevent tissue damage
19
Q

Steps of inflammation

A
  1. macrophages recognize pathogen and release histamine, substance P and other mediators/cytokines.
  2. Vasodilation, leakage of plasma proteins and fluids to infected tissues
  3. recruitment of monocytes to site of infection.
  4. Phagocytosis of pathogen by macrophages.
  5. Edema ( swelling), redness, pain, warming
20
Q

Phagocytosis and destruction of microbial pathogens

A
  • achieved by pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), which bind to pathogen associated molecular patterns (PAMPs) on the surface of microbes.
  • The successful ingestion of the microbe is followed by its destruction by lysosomal enzymes, reactive oxygen species (ROS), and nitric oxide (NO).
21
Q

Neutrophils have additional mechanisms of microbial killing such as

A

1) the release of their antimicrobial granule contents into the extracellular environment
2) the shedding of their chromatin (DNA+Histone) forming neutrophil extracellular traps (NETs) which can trap microbes and kill them.

22
Q

Antiviral immune response

A
  1. Type I interferons: IFN-α and IFN-β ( secreted by virus-infected cells.
    • basis for the use of IFN to treat viral hepatitis such as Hepatitis C (HCV).
  2. NK cells are innate lymphoid cells - directly kill virus-infected cells/cancer cells/ cells that are precoated with antibody.
    • cytoplasmic granules- do not express T cell receptors nor prouce antibodies
  3. The IFN-γ secreted by NK cells enhance the phagocytic activity of macrophages; IL-12, IL-15 (important for development and maturation of NK cells), and type I- IFN activate NK cells
23
Q

Adaptive Immunity

A
  • mounted only after first exposure to the pathogen.
  • Adaptive immune system consists of lymphocytes (B and T cells) and the product of B cells; antibodies.
  • Any molecule that is recognized by antibodies or T and B lymphocytes is called an antigen.
24
Q

Types of adaptive immunity

A
  • Humoral (antibody mediated, involves B cells)
  • cell mediated immunity (mediated by T cells).
25
Q

Humoral (antibody-mediated) Immunity

A
  • Effector Mechanism : Antibodies produced by B cells enter blood and body fluids including secretions (for IgA=secretory antibody)
  • Responding B lymphocytes
  • neutralize the infectivity of microbial pathogens and their toxins.
  • Antibodies can only bind to extracellular microbes and block infections.
26
Q

Cell mediated immunity

A
  • defense against intracellular pathogens such as viruses and intracellular bacteria as well as cancer.
  • (Th1 cells) can activate phagocytes (macrophages) to destroy intracellular pathogens
  • Other type of T cells (cytotoxic T lymphocytes (CTL) or TC) can destroy virus infected or cancer cells.
27
Q

Clonal Selection

A
  • lymphocytes specific for many different antigens are developed without any prior exposure to the cognate antigen
  • Each antigen will activate the lymphocytes which are specific to that particular antigen (lymphocyte clone).
  • lymphocytes that are specific to a particular antigen are called naïve lymphocytes
  • Once they get activated by encountering the antigen, they differentiate into effector lymphocytes.
28
Q

primary immune response

A

on first exposure to an antigen

29
Q

secondary immune response.

A
  • more effective and rapid response upon second exposure
  • due to the activation of memory lymphocytes which are long lived and can respond to the same antigen in a rapid manner.
30
Q

antigen presenting cells

A

dendritic cells, macrophages, and B cells

31
Q

effector cells

A
  • lymphocytes either T or B cells,
  • macrophages and granulocytes e.g. neutrophils.
32
Q

Lymphocytes

A
  • T and B lymphocytes
  • Special recognition of antigens :
    • Humoral ( B lymp)
    • Cell-mediated (T lymp)
33
Q

naïve B lymphocytes

A
  • the cognate antigen differentiate into antibody secreting cells (plasma cells), with the help of T helper cells.
  • neutralize microbes, phagocytosis, complement activation
34
Q

T helper lymphocytes

A
  • recognize antigen presented by antigen presenting cells
  • secrete cytokines which mediate different immune reactions including B cell differentiation to plasma cells.
  • Activation of macrophages; inflammation; Activation proliferation and differentiation of T and B lymphocytes.
35
Q

Cytotoxic T lymphocytes (CTLs)

A

are specialized in recognizing antigens presented by infected cells (virus infected) or cancer cells, and kill them.

36
Q

Regulatory T lymphocytes (Tregs)

A

downmodulate any exaggerated immune reactions and prevent autoimmunity.

supress immune response

PBS 602 Pathophysiology (13 decks)

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