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Biology 102 > Lecture 11 - Immune System > Flashcards

Lecture 11 - Immune System Flashcards

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1
Q

Three Stages of Defense

A
  1. recognition phase
    - organism distinguishes from self and non-self
  2. activation phase
    - recognition leads to mobilization of cells and molecules to fight the invader
  3. effector phase
    - mobilized cells and molecules destroy the invader
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2
Q

Two Types of defense mechanisms

A
  1. Innate immune system
    - nonspecific defenses
    - first line of defense
    - recognize a broad class of organisms or molecules
    - act very rapidly (minutes to hours)
    - several forms (skin, molecules toxic to invaders, phagocytotic cells that digest invaders)
  2. adaptive immune system
    - specific defenses
    - aimed at specific pathogens
    - slow to develop (days, weeks) and long lasting
    - humoral immune response (b-cells produce antibodies)
    - cellular immune responce (killer t cells)
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3
Q

Innate Immune System In General

A
  • nonspecific defenses
  • first line of defense
  • “ready to go”
  • recognize a broad class of organisms or molecules
  • act very rapidly (minutes to hours)
  • several forms (skin, molecules toxic to invaders, phagocytotic cells that digest invaders)
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4
Q

Adaptive Immune system

A
  • specific defenses
  • aimed at specific pathogens
  • slow to develop (days, weeks) and long lasting
  • humoral immune response (b-cells produce antibodies)
  • cellular immune responce (killer t cells)
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5
Q

Lymph

A
  • fluid in intracellular spaces throughout the body that circulates through lymphatic vessels
  • when blood exchanges nutrients and metabolites with tissue, it does so via the interstitial fluid
  • some of the fluid is reabsorbed into blood vessels
  • some is collected into lymph capillaries where it moves slowly through vessels of lymphatic system as lymph
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6
Q

Lymph Nodes

A
  • sites along lymph vessels that contain white blood cells embedded in connective tissue
  • as lymph passes through a lymph node, white blood cells encounter foreign cells and molecules that have entered the body and can initiate an immune response
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7
Q

White blood cells

several types

A
  • circulate through blood and lymph
  • originate from stem cells in bone marrow

Types:

  • phagocytes (macrophages, dendritic cells)
  • Lymphocytes (b cells, t cells, natrual killer cells)
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8
Q

Antibodies

A
  • proteins that bind specifically to certain substances that are non-self
  • can inactivate the pathogen
  • can act as a tag to make it easier for immune system to attach
  • produced by b cells
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9
Q

Major histocompatibility complex

A
  • proteins found on surface of most cells of the body
  • self-identifying labels
  • can present non-self substances
  • coordinate interactions between lymphocytes and macrophages
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10
Q

T cell Receptors

A
  • membrane bound proteins on surface of t cells

- recognize and bind to non-self substances presented by MHC molecules on surface of other cells

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11
Q

Cytokines

A
  • soluble signaling proteins that are released by many cell types
  • bind to cell surface reseptors
  • can activate or inactivate B cells, macrophages, T cells
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12
Q

Physical Barriers of the innate immune system

A

SKIN
- difficult for pathogens to penetrate skin

MUCUS

  • traps airborne microorganisms
  • contains the enzyme lysozome (destroys bacteria by breaking down their cell walls)
  • contains the peptide defensin (hydrophobic peptides that insert into cell wall of microorganism and make the membranes permeable)

TEARS, SALIVA
- lubricate and cleanse

GASTRIC JUICE

  • very acidic (HCl)
  • proteases
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13
Q

cellular and chemical defenses of innate immune system

A

once pathogen has penetrated the body, it encounters defenses such as the activation of defensive cells and secretion of various defensive proteins

  • compliment proteins
  • interferons
  • normal bacterial flora of the body
  • phagocytes
  • natural killer t cells
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14
Q

Compliment Proteins

A
  • more than 20 different proteins
  • bind to microbe to help phagocytes recognize and destroy it
  • activate inflammation response and attract phagocytes to site
  • lyse invading cells
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15
Q

interferons

A
  • type of cytokine
  • increase resistance of neighboring cells to infection
  • stimulate cells to hydrolyze bacterial or viral proteins
  • inhibit viral replication if cells are subsequently infected
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16
Q

Normal Bacteria Flora

A

(defensive cells)

  • some bacteria normally live in our body without causing disease
  • compete with pathogens for space and nutrients
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17
Q

phagocytes

A

(defensive cells)

  • Ex: macrophages
  • pathogenic bacteria and viruses can be recognized by phagocytes and ingested
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18
Q

Natural killer cells

A

(defensive cells)

  • type of lymphocyte
  • can distinguish virus-infected cells and some tumor cells from thrig normal counterparts
  • initiate apoptosis or lysis of these target cells
19
Q

Defense from inflammatory response

A
  • coordinated defense response to infection or injury
  • tissue damage recruits mast cells
  • mast cells release histamine and prostaglandins (cause blood vessels to dilate and become leaky –> heat and inflammation)
  • complement proteins leave blood vessels and attract phagocytes
  • phagocytes engulf invading pathogen and dead cells
  • produce cytokines (signal barin to produce fever, stimualtes immune cell production and function)
20
Q

Why is inflammation painful?

A
  • increased pressure due to swelling
  • prostaglandins increase sensitivity of nerve endings to pain
  • aspirin: inhibits prostaglandin synthesis
21
Q

Four main features of the adaptive immune system

A

SEPCIFICITY
- antibodies (produced by B-cells) and t-cell reseptors recognize and bind to sepcific sites (epitopes) on sepcific pathogens –> antigens

DISTINGUISHING SELF FROM NON SELF

  • important to not attack the cells of the own body
  • aby b or t cells that show potential to mount immune response against self-proteins are killed early on in that cells development

DIVERSITY

  • pathogens can take many forms (many strains of ciruses, bacteria, protistsm fungi, parasites)
  • humans can respond to ~ 10 million different atigens

IMMUNOLOGICAL MEMORY
- after responding to a particular pathogen once, immune system can respond more rapidly and powerfully to the same threat in the future

22
Q

Two Major Types of Specific Responses (Adaptive immunity)

A

HUMORAL IMMUNE RESPONSE

  • produces antibodies
  • with goal of destroying the pathogen itself
  • main player: B-cells (produce antibodies)

CELLULAR IMMUNE RESPONSE

  • destrosy infected cells
  • main player: cytotoxic (killer) T cells
  • operate simultaneously
  • share many mechanisms
23
Q

Antigen Presentation and Helper T Cells

first step in adaptive immunity

A

(first step for both humoral and cellular response)

Antigen presenting cell (APC)

  • includes dendritic cells and macrophages
  • T-cells cannot recognize free-floating antigen
  • APCs capture antigens and enable their resognition by “presenting” them
  • antigen is take up by an APC cell and processed (digested)
  • a piece of this digested pathogen (antigen) is displayed by the APC outside the APC cell on a major histocompatibility complex (MHC molecule)

T Helper Cell

  • binds to the antigen on APC
  • releases cytokines
  • Th cell stimulates both the humoral and cellular immune responses
24
Q

Major histocompatibility complex (MHC) proteins present antigens (second step in adaptive)

A
  • cell surface protein that presents antigens to T cells
  • T-cells only recognize presentation of non-specific cells
  • aldo used to ID whether the cell itself is from the host (many different MHC alleles, transplant rejection)
25
Q

Types of MHC cells

A

Class I MHC Complex

  • present on surface of all cells in the body
  • when cellular proteins are degraded, fragments are carried to plasma membrane and presented on MCI outside of cell
  • sampling of all components in the cell, normal or not
  • detects infections of mutations
  • recruits cytotoxic (killer) T cells

Class II MHC compelx

  • found on surface of APCs
  • when the APC ingests a pathogen through phagocytosis, the pahtogen is broken down and a fragment is carried to the cell surface
  • recruits helper T cells
26
Q

Humoral Immune Response

A
  • B cells make antibodies (can secrete them or express them on cell surface, bind to specific antigen)
  • first time antigen is encountered, it is detected by binding to the antibody receptors on the B-cell surface (with help from Th cells)
  • activates B-cell to make and secrete multiple copies of the antibody
27
Q

Antibodies

A
  • all have a common structure
  • tetramer of 4 polypeptide chains
  • two are identical light chains
  • 2 are identical heavy chains

Each chain has 2 regions

  1. constant regions
    - shared amino acid sequences
    - determine whether it will be an integral membrane receptor or a soluble antibody secreted into the blood stream
  2. variable regions
    - different for each type of antibody
    - specificity of antigen binding
    - two identical antigen binding sites on each antibody
28
Q

Selective proliferation of B-cells

A
  • one B-ell makes a specific type of antibody
  • enormous diversity of different B-cells exist, each of which makes a different type of antibody
  • one antibody reacts with a specific antigen

Proliferation

  • when an antigen binds to a B-cell, it (with Th cells) stimulates it to proliferate to form a group of identical C cells
  • all of these clones produce and secrete antibpdies with that same sepcificity as the activated B-cell
29
Q

Humoral Immune Response: Part I

A

Activation: sepcific Th cells are activated and proliferate

  • APC presents antigen via Class II MHC complex
  • T helper cell binds to APC
  • specific receptor that binds specific antigen
  • Th cell releases cytokines
  • cytokines activate Th cell to proliferate, producing clones of Th cells with the same specificity
30
Q

Humoral Immune Response: Part II

A

Effector phase: activated Th cells activate specific B cell to proliferate and produce antibodies for secretion

B Cells act as APCs

  • B cells have antibodies bound to cell surface that serve as receptors to which antigens can bind
  • pathogen binding to this antibody is internalized and broken down and antigen is displayed by MHCII complex of B cell
  • activated Th cell binds to a Bcell that is presenting the correct antigen (same antigen as it originally encountered in the initial APC)
  • cytokines released by Th cells activate B cells
  • activated B-cell proliferates and synthesizes antibodies
31
Q

Humoral Immune Response Part III

A

Th cell stimulates B Cell to divide, differentiate and produce antibodies

Gives rise to two types of B cells:

  1. effector B cells (plasma cells)
    - secrete antibodies into bloodstream
    - all effector cells arising from a given B cell produces antibodies that are specific for the antigen that originally bound to the parent B cell
  2. Memory cells
    - long lived stand by’s that are ready to amp-up the immune system quickly if re-exposed to a pathogen
    - allow for lasting immunity against pathogen
32
Q

Antibody function

A

OPSONIZATION

  • antibody stimulates removal of pathogen by macrophages
  • tag a microbe or an infected cell for phagocytosis

NEUTRALIZE TARGET
- block pathogen’s ability to enter cells

AGGLUTINATION

  • link pathogens together into large complexes
  • become easy targets for phagocytes

TRIGGERING OTHER IMMUNES PATHWAYS SUCH AS COMPLEMENT SYSTEM

  • marks pathogen for phagocytes
  • helps kill the pathogen directly
33
Q

Cellular Immune Response Part I

A
  • cell that has been infected by a virus or undergone mutations will contain foreign or abnormal peptides
  • will present these on cell surface as Class I MHC complex
  • Cytotoxic T cells recognize and bind to this comples
  • Tc cell activation and growth is promoted by activated T cells
  • activation of a specific T cell triggers selective proliferation of that type of T cells
  • these activated Tc cells now bind to any cell tha tis displaying an antigen on its Class I MHC receptor (and therefore is infected)
34
Q

Cellular Immune response Part II: TC cells kill infected cells

A

CELL LYSIS

  • activated Tc cells produce a substance called perforin
  • peprforin lyses the cells that the Tc cell has bound to via MHC I complex

PROGRAMMED CELL DEATH
- Tc cells can also bind to a different receptor on the target cell that initiates apoptosis in that cell

  • work together to eliminate antigen containing host cell
  • help rid body of its own virus-infected cells
35
Q

What allows for long Lasting Immunity

A
  • activated lymphocytes (B or T cells) divide and differentiate to produce two types of daughter cells

EFFECTOR CELLS

  • carry out attack on antigen
  • effector B cells secrete antibodies
  • effector t cells secrete cytokines and other molecules that destroy pathogen cell
  • only live a few days

MEMORY CELLS

  • long lived cells
  • retain ability to start dividing on short notice to produce more effector and memory cells
  • many survive in body for decades
36
Q

Two stages of immune response to an antigen

A
  1. Primary
    - when body first recognizes an antigen, naive lymphocytes that recognize the antigen proliferate
    - lag time - takes a while for number of B and T cells to slowly increase
  2. Secondary
    - subsequent encounters with the same antigen
    - memory cells bind antigen and rapidly proliferate
    - launch army of B and T cells
    - much more rapid and powerful response
37
Q

Where does immunity come from?

A
  • can come from previous exposure to pathogen

- can come from vaccines

38
Q

Immunity from Vaccines

A

introduction of the antigen into the body in a form that doesnt cause disease

Ways:
INACTIVATION
- kill pathogen with heat or chemicals

ATTENUATION

  • live but not toxic
  • cultured in the lab to get mutations that make it harmless

PEPTIDE SUBUNIT

  • recombinant DNA technology
  • do not introduce a whole microorganism to the immune system, just a part of the antigen protein
  • peptide fragments that can bind and activate lymphocytes but do not have the harmful part of a protein

Then:

  • initiate primary immune response, generating memory ells without making the person ill
  • memory cells already exist if person encounters pathogen later
39
Q

What happens when the immune system malfunctions?

A
  • overreact (allergic reaction)
  • attack self antigens (autoimmune)
  • function weakly (immune defficiency)
40
Q

Allergic reaction

A
  • immune system overreacts to a dose of antigen
  • exposure to an antigen causes B-cells to make a large amount of a specific type of antibody that takes up residence in cell membrane of mast cells
  • if individual is re-exposed to that allergen, the allergen binds to these antibodies on the mast cells
  • causes the mast cells to secrete a large amount of histamine
  • dilation of blood vessels, inflammation
41
Q

autoimmune disease

A

T cells or antibodies that bind self-antigens

  • during development of lymphocytes, cells that make antibodies against self antigens that should have been destroyed were not
  • molecular mimicry - T cells that are designed to recognize a non-self antigen may accidentally recognize something in he self antigen that has a similar structure
42
Q

Immune deficiency disorder

A
  • highly vulnerabel to infections and cancer
  • B or t cells never form
  • B cells lose ability to give rise to effector cells
  • HIV (aids)
  • infects and destorys helper T cells
  • killed by both the virus itself and Tc cells the destroy infeted cells
43
Q

Examples of autoimmune disease

A

Lupus
- b cells produce antibodies against the body’s own nuclear proteins

rheumatoid arthritis

  • inability to shut down a t cell response
  • inflammation in the joints

hashimoto’s thyroiditis
- immune cells attack thyroid tissue, resulting in fatigue, depression, weight gain

type i diabetes
- immune reaction against cells in pancreas that produce insulin

MS
- immune system attacks and damages myelin

myasthenia gravis

  • antibodies block acetylcholine receptors on muscle cells
  • muscle weakness

Biology 102 (15 decks)

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