Chapter 13 Host Defenses

Innate defense

non-specific defenses used to protect the body from any general pathogenic attack

Acquired defenses

specific defenses used to protect the body from pathogens identified by the body

Specific Immunity

body’s ability to recognize and react to a specific invader

• Has a “memory” to respond rapidly to an infection the second time it happens

Antigen

anything that stimulates a specific immune response

epitope

the 3D region of an antigen that is actually recognized by the immune system

Exogenous antigens

found on invaders that exist outside the host cell

• Bacterial infections

• Parasitic worms

• The immune system encounters these directly

Endogenous antigens

found on invaders that exist inside body cells

• Viruses once they’ve entered the host cell

• Obligate intracellular parasites

• The immune system can’t detect these directly

• To be detected by the immune system, the antigens must be incorporated into the host cell membrane

Autoantigens

antigens that are naturally found on host cell

• Immune cells need to ignore these

• Because these autoantigens label the cell as “self”

autoimmunity

If auto auto antigens aren’t destroyed this leads to ___

• bad

Antibodies

 proteins used by the immune system to identify, bind to, and in many cases help attack an invading organism

Lymphocytes

one of the types of Leukocytes (WBCs)

• Lymphocytes are made by stem cells in bone marrow

B Lymphocytes

Some mature in the Bone marrow

T Lymphocytes

Some mature in the Thymus

Plasma Cells

B lymphocytes when active

• Makes a lot of copies of itself

• Makes and secretes many many copies of a specific antibody

(the one that recognized the ‘correct’ antigen)

Cytotoxic T cells

Secrete cytokines that trigger replication

• Make more copies of that particular ‘model’ of T cyt cell

• Kill ‘bad’ cells by inducing apoptosis

Helper T cells

1. Secrete cytokines that trigger replication

   1. Make more copies of that particular ‘model’ of T cyt cell

2. Kill ‘bad’ cells by inducing apoptosis

Major Histocompatibility Complex

type of protein that is found on the surface of body cells

• allows the body cells to alert the immune system that there is an invader present

• MHC does this by holding antigens on the surface of the cell to ‘show’ it to T cells

MHC-I

found on the membranes of all nucleated body cells

•  “Look what I made”

• “there is an intracellular pathogen inside this cell”

• displays endogenous antigens 

MHC-II

 present only in antigen-presenting cells

• “Look what I ate”

• displays exogenous antigens to helper T-cells

Humoral Response

an immune response against exogenous antigens

• Response occurs in the blood via antibodies

Process of the Humoral Response

1. Antigen presentation

2. Helper cell differentiation

3. Clonal selection

4. B cell activation

5. Memory

interleukins

The interaction between the APC and the Tₕ cell causes a release of ___ that activate the Helper T cell

Clonal selection

the process that selects for a particular ‘version’ of the B cell that can recognize the antigen

• The body is acknowledging that this version of the B cell is important to have right now

Cell-Mediated

Response is an immune response against endogenous antigens

• Things that are found inside a host cell

• This is a response to kill infected or abnormal cells

Naturally-acquired immunity

gained in response to antigens encountered in daily life

Artificially-acquired immunity

gained in response to antigens introduced via vaccine

Active immunity

response to antigens via humoral or cell mediated response

Passive immunity

response to antigens via antibodies that came from another individual

Immunization

 introduction of artificially-acquired immunity

passive immunization

used by giving individuals specific antibodies against a thing

• doesn’t train the immune system

Herd Immunity

the idea that a population is what needs to be protected from a disease, rather than any single individual

attenuated vaccine

Live organisms (bacterium or virus) that has been modified is introduced to a person

• can be through genetic modification or by selecting mutants that are virulent

• modification makes the organism avirulent

Killed vaccines

may either be whole killed microbes or they can be subunits or fragments of a microbe

toxoid vaccine

The toxoid is a modified version of the toxin

(This is important for a few diseases)

• Tetanus

• Diphtheria

make an mRNA vaccine

1. What does an antigen on the surface of the pathogen look like?

2. What is an RNA sequence that would generate that structure?