Lecture 21 Immune system

Question 1

innative immunity

Answer 1

Each of a small set of receptors recognize a molecule absent from animals, but common to a type of pathogen

all animals have innative immunity, a defense active immediately upon infection
innate immuity includes barrier defenses (slide 6)

Question 2

adaptive immunity

Answer 2

a sophisticated and precise defense mechanism in vertebrates, including humans, that provides a tailored response to specific pathogens or antigens. This type of immunity is highly specialized and develops throughout an individual’s life as a response to exposure to various pathogens, vaccines, or environmental factors.
(specificality and memory)

Each of a vast number of receptors is specific for a particular part of a protein in one pathogen, such as a surface protein of the influenza virus

The adaptive immune response is activated after the innate response and develops more slowly. (slide 6)

Question 3

immune system functions

Answer 3

● Protects against pathogens:
○ Bacteria
○ Viruses
○ Parasites

● Protects against foreign molecules (e.g., toxins)

● Removes dead or damaged cells

● Attempts to recognize and remove abnormal cells

Question 4

nonspecific immunity

Answer 4

does not target specific pathogen
-physical barriers
-inflammatory process

Question 5

specific immunity and what types are there

Answer 5

identifies specific pathogen

-natural immunity: (innate) like allergies
recognition of traits shared by broad ranges of pathogens, using a small set of receptors

rapid response

-acquired immunity: active or passive
recognition of traits specific to particular pathogens, using a vast array of receptors

slower response

Question 6

innate immunity defenses

Answer 6

barrier defenses: skin, mucous membranes, secretions

internal defenses: phagocytic cells natural killer cells, antimicrobial proteins, inflammatory response

Question 7

what are the 2 adaptive immunity responses

Answer 7

humoral response: antibodies defend agains infection in body fluids

cell-mediated response: cytotoxic cells defend agains infection in body cells

Question 8

innate immunity overview

Answer 8

● First-line defenses are barriers blocking entry If invaders breach, sensor systems detect
*Physical barriers - Skin and mucous membranes

● Sensor systems –
○ Sentinel cells use PRR (Pattern Recognition
Receptors) in cell membrane and cytoplasm
○ Complement system

● Innate defenses effectors work to destroy invaders
○ Interferons
○ Phagocytosis
○ Fever

Question 9

Barrier defenses

Answer 9

● Skin and mucous membranes of the
respiratory, urinary, and reproductive tracts.

● Mucus traps and allows for the removal of microbes.

● Many body fluids including saliva, mucus, and tears are hostile to many microbes.

● The low pH of skin and the digestive system prevents growth of many bacteria.

Question 10

Cellular Innate Defenses

Answer 10

Innate immune cells in mammals detect, devour, and destroy invading pathogens.

These cells recognize groups of pathogens using TLRs, or Toll-like receptors.

TLRs recognize fragments of molecules characteristic of a set of pathogens.

Question 11

Hematopoietic stem cells (HSC found in bone marrow)

Answer 11

precursors where blood cells originate from

Question 12

HSC maturing

Answer 12

Cytokines induce HSC to mature - Colony-Stimulating Factors (CSFs)
● Move around body, travel through circulatory systems
● Always found in normal blood increase during infections
● Some reside in various tissues

Question 13

general categories for cells of the immune system

Answer 13

● Red blood cells (erythrocytes) carry O2
● Platelets (from megakaryocytes) involved in clotting
● White blood cells (leukocytes) important in host defenses

Question 14

what are the 4 types of Leukocytes (white blood cells)

Answer 14

● Granulocytes
● Mononuclear Phagocytes
● Dendritic Cells
● Lymphocytes

Question 15

granulocytes

Answer 15

contains cytoplasmic granules

● Neutrophils highest numbers, engulf and destroy bacteria,
other material (phagocytes)
● Basophils involved in allergic reactions, inflammation
– Mast cells similar; found in tissues, release histamines
● Eosinophils fight parasitic worms
– Also involved in allergic reactions

Question 16

Monocytes

Answer 16

● Comprise mononuclear phagocyte
system (MPS)
● Monocytes (circulate in blood) and
cell types that develop as they
leave blood stream
● Dendritic cells and Macrophages
differentiate from monocytes

Question 17

Lymphocytes

Answer 17

● Responsible for adaptive immunity
● B cells, T cells - specific in recognition of antigen
● Generally reside in lymph nodes, lymphatic tissues
● Natural killer (NK) destroy certain types of cells

Question 18

Phagocytosis

Answer 18

the ingestion and digestion of foreign
substances including bacteria.

Question 19

what are the 2 main types of phagocytic cells

Answer 19

these cells engulf and destroy pathogens, in mammalian body

• Neutrophils circulate in the
  blood
• Macrophages migrate
  through the body or reside
  permanently in organs and
  tissues (slide 19)

Question 20

Toll-like receptors: TLR

Answer 20

TLRs recognize fragments of
molecules characteristic of a set
of pathogens.

Question 21

Inflammatory response

Answer 21

as pain and swelling, is brought
about by molecules released upon
injury or infection.

Question 22

Mast cells

Answer 22

immune cells found tissues, release histamine, which triggers blood vessels to dilate and become more permeable (part of inflammatory response)

Question 23

Local inflammatory response

Answer 23

1.Mast cells release histamines.
Capillaries dilate.

2.Neutrophils and anti- microbial
peptides enter tissue.

3.Neutrophils digest
pathogens and cell debris.
Tissue heals.

Question 24

Inflammation - Cascade of events

Answer 24

1. Dilation of small blood vessels
   ● Greater blood flow (heat, redness); slower flow rate
   ● Leakage of fluids (swelling, pain)
2. Migration of leukocytes from bloodstream to tissues
   ● Endothelial cells “grab” phagocytes, slow them down
   ● Phagocytes squeeze between cells of vessel (diapedesis)
3. Clotting factors wall off site of infection
4. Dead neutrophils, tissue debris accumulate as pus

Question 25

what causes inflammation?

Answer 25

Tissue damage results in inflammation ● Purpose is to ○ contain site of damage, ○ localize response, ○ eliminate invader ○ restore tissue function

Question 26

what are the 5 signs of inflammation

Answer 26

Results in 5 signs ○ swelling, ○ redness, ○ heat, ○ pain, sometimes loss of function

Question 27

Cardinal signs of inflammation

Answer 27

1. Rubor (redness) - increased blood flow 2. Tumor (swelling) - exudation of fluid 3. calor (heat) - increased blood flow, exudation of fluid, release of inflammatory mediators 4.Dolor(pain) - stretching of pain receptors and nerves by inflammatory exudates, chemical mediators 5. Functio laesa (loss of function) - pain, disruption of tissue structure, fibroplasia and metaplasia

Question 28

local vs systemic inflammation

Answer 28

Acute inflammation ● short term ● mainly neutrophils ● macrophages clean up damage by ingesting dead cells and debris If acute fails Chronic inflammation ● macrophages, giant cells accumulate, ● granulomas form

Question 29

Fever - an important host defense mechanism

Answer 29

Strong indicator of infectious disease, especially bacterial ● Temperature-regulation center in brain normally holds at 37°C but raises during infection in response to pyrogens (fever inducing substances) ● Growth rates of bacteria optimized for 37°C typically drop sharply above optimum, allows more time for defenses ● Moderate temperature rise increases rates of enzymes ● Enhances inflammatory response, phagocytic killing, multiplication of lymphocytes, release of attractants for neutrophils, production of interferons and antibodies, release of leukocytes from bone marrow ● White blood cells (macrophages) release chemicals that increase body’s temperature ● Divert blood from superficial blood vessels to body core – increase To ● 102-104oF (39-40oC)

Question 30

Adaptations - Evasion of Innate Immunity by Pathogens

Answer 30

Modifying their surface to prevent recognition or phagocytosis * Streptococcus pneumonia (meningitis) - outer capsule Resisting breakdown following phagocytosis * Mycobacterium tuberculosis -Tuberculosis (TB), another such disease, kills more than a million people a year

Question 31

Adaptive Immunity

Answer 31

aka Acquired immune response ● activated later ● slow response ● Relies on lymphocytes

Question 32

Receptors provide pathogen-specific recognition (what cells relate to this)

Answer 32

The adaptive response relies on two types of lymphocytes, or white blood cells: ● T-cells - mature in the thymus, above the heart ● B cells -mature in bone marrow

Question 33

What are antigens?

Answer 33

● substances that can elicit a B or T cell response ● T or B cells bind to antigens via antigen receptors specific to part of one molecule of that pathogen. ● The small, accessible part of an antigen that binds to an antigen receptor is called an epitope.

Question 34

Antigen Recognition by B Cells and Antibodies

Answer 34

Each B cell antigen receptor is a Y-shaped molecule ● 2 identical heavy chains ● 2 identical light chains. 2 regions ● Constant (C) regions of the chains vary little ● Variable (V) regions differ greatly. Provide antigen specificity.

Question 35

Binding of an antigen activated B cells.

Answer 35

● B cell binds to epitope ● This gives rise to cells that secrete a soluble form of the protein called an antibody or immunoglobulin (Ig). ● Different Ab recognize different epitopes

Question 36

T cell antigen receptor

Answer 36

T cells bind to antigen fragments displayed or presented on a host cell. These antigen fragments are bound to cell-surface proteins called major histocompatibility complex (MHC) molecules. MHC molecules are host proteins that display the antigen fragments on the cell surface.

Question 37

Adaptive immunity has 2 components

Answer 37

the humoral immune response: (b cell) protects blood the cell-mediated immune response: (t cell) destroy infected host cells

Question 38

Cytotoxic T cells (type of T cell)

Answer 38

–TC induces apoptosis: proteases, cytotoxins (perforin) –Releases cytokines to alert other cells –Example - CD8

Question 39

Helper T cells (type of T cell)

Answer 39

–Activates macrophages – giant cells –Activate B cells –Produce cytokines to direct and support T cells –Example - CD4 CD4 is receptor for HIV, which infects TH cells

Question 40

Natural killer cells (type of T cell)

Answer 40

–Killing of infected cells tagged with antibodies –Secrete IFN-gamma that stimulates macrophages

Question 41

Cytotxic T cells

Answer 41

use toxic proteins to kill cells infected by viruses or other intracellular pathogens before pathogens fully mature Activation requires: ● signals from helper T cells ● interaction with an antigen-presenting cell (APC). Fragments of foreign proteins produced in infected host cells associate with class I MHC molecules and are displayed on the cell surface, where they can be recognized by activated cytotoxic T cells.

Question 42

What do T-Helper Cells do (steps)

Answer 42

activates humoral and cell-mediated immune responses. 1. a foreign molecule must be present that can bind specifically to the antigen receptor of the helper T cell. 2. this antigen must be displayed on the surface of an antigen-presenting cell (APC) ie dendritic cell, macrophage, or B cell.

Question 43

Activation of B Cells

Answer 43

Activation of B cells involves helper T cells and proteins on the surface of pathogens. When an antigen binds a B cell, the cell takes in a few foreign molecules by receptor-mediated endocytosis. The class II MHC protein of the B cell then presents an antigen fragment to a helper T cell, a process that is critical to B cell activation.

Question 44

Antibody Function

Answer 44

● Antibodies do not kill pathogens; instead, they mark pathogens for inactivation or destruction. ● In neutralization, antibodies bind to viral surface proteins, preventing infection of a host cell. ● Opsonization - promotion of phagocytosis

Question 45

Activation of B cells

Answer 45

slide 46

Question 46

Humoral and Cell-Mediated Immune Responses

Answer 46

Both the humoral and cell-mediated responses can include primary and secondary immune responses. Memory cells enable the secondary response.

Question 47

Immunological Memory

Answer 47

Immunological memory is responsible for long-term protections against diseases.

Question 48

Primary immune response

Answer 48

represents the first exposure to a specific antigen a clone of lymphocytes

Question 49

Secondary immune response

Answer 49

memory cells facilitate a faster, more efficient response

Question 50

types of adaptive immunity

Answer 50

slide 54

Question 51

immunization

Answer 51

Passive artificial The projection provided by a second immune response provided the basis for immunization. Antigens are artificially introduced into the body to generate adaptive immune response and memory cell formation. Immunizations are carried out with vaccines, preparations of antigens from many sources. Vaccination programs have been successful against many infectious diseases.

Question 52

Not all cells have the saem genome

Answer 52

slide 59 and 60

Question 53

Generation of B and T Cell Diversity

Answer 53

● By combining variable elements, the immune system assembles millions of different antigen receptors from a small number of parts. ● An immunoglobulin (Ig) gene encodes the light chain of the B cell receptor. ● Many different chains can be produced from the same gene by rearrangement of the V, J, and C regions.

Question 54

Immunoglobulin (antibody) gene rearrangement

Answer 54

slide 62

Question 55

adult stem cells

Answer 55

Many early embryos contain stem cells capable of giving rise to differentiated embryonic cells of any type. Adult stem cells can generate multiple (but not all) cell types and are used in the body to replace nonreproducing cells as needed. (slide 64)

Question 56

5. Adaptive immunity is blocked or misregulated (allergies)

Answer 56

Exaggerated (hypersensitive) responses to certain antigens called allergens.

Question 57

Adaptive immunity is blocked or misregulated (autoimmune disease)

Answer 57

● Immune system is active against particular molecules of the body ● Loss of self-tolerance has many form ○ Lupus - histones and DNA released by the normal breakdown of body cells. These self-reactive antibodies cause skin rashes, fever, arthritis, and kidney dysfunction. ○ Type 1 diabetes - insulin-producing beta cells of the pancreas ○ Multiple sclerosis - myelin sheaths that encase many neurons

Question 58

Adaptive immunity is blocked or misregualted (HIV Virus)

Answer 58

slide 69 ad 70

Question 59

natural immunity:

Answer 59

-natural immunity: (innate) like allergies recognition of traits shared by broad ranges of pathogens, using a small set of receptors rapid response

Question 60

acquired immunity:

Answer 60

active or passive recognition of traits specific to particular pathogens, using a vast array of receptors slower response