I&I Adaptive Immune Response to Pathogens

What Innate Immune cells respond when a microbe is in the extracellular?

Phagocytic cells

What innate immune cells that respond to a microbe in the intracellular of a cell?

NK cells

What adaptive immune cells/products that will be generated to fight a microbe in the extracellular space?

B-cells and Antibody production

What adaptive immune cells/products that will be generated to fight a microbe in the intracellular space of a cell?

CTLs and DTH

What does DTH stand for?

Delayed-type Hypersensitivity

What sites of infection are considered the extracellular?

Interstitial spaces

Blood

Lymph

Epithelial surfaces

What organisms are most likely going to create infection in the e

What are the site of infections that are considered the intracellular?

Infected Host cell

Engulfed by phagocytic cell and can replicate

What organism are most likely going to cause infection in the intracellular space?

Viruses

Bacteria

Protozoa

What is a facultative pathogen?

A pathogen that can be either extacellular or intracellular depending on the conditions

How can intracellular pathogen become extracellular pathogens?

When they enter or leave the host cell

What is an example of a pathogen that has a complex life cycle where some stages are extracellular and some are intracellular?

Helminths

What ensures that an extracellular pathogen infection generates a dominate Adaptive Humoral immune Response?

T-helper cells ensure that the humoral immune response dominates in the extracellular infections.

How does T-helper cells ensure that the humoral immune response dominates in the extracellular infections?

Using pro/semi-pro APCs present to Th-cells using MHC-II

What ensures an intracellular pathogen infection generates a dominated adaptive mediated immune response?

Generating antigen-specific CTLs dominates with intracellular infections

How does CTLs know which cells to attack?

Host cells present to CTLs using MHC-I

What receptor does T-Helper cells express on their surface?

CD4

What receptor does CD4 on the T-Helper cell recognize on the APC?

MHC-II

What does the binding of MHC-II and CD4 mean for the T-Helper cells?

ensures that the T-helper cells are activated by the peptides form the protein engulfed form the extracellular space.

Once the T-Helper cells are activated via the peptide on the APC what do they do to fight the extracellular microbe?

T-Helper will release cytokines to help the B-cells make antibody that target the microbe outside the cell.

What is the receptor that CTLs express on their surface?

CD8

What receptor does CD8 on the CTL recognize on the host cell with a nuclei?

MCH-I

What does the binding of MHC-I and CD8 ensure for the CTL?

That CTLs are activated by host infected cells

What type of microbes molecules are processed for presentation to intiated by extracellular antigens?

Proteins

What fragments are presented to initiated by the extracellular microbial antigen?

Peptides

What cells presents the antigen that is initiated by extracellular microbial antigens?

Pro/semi-pro APC (dendritic cells, Macrophages, B-cells)

What cells respond to the presented antigen when initiated by extracellular microbial antigens?

T-Helper cells

What MHC molecule is used to present the antigen when initiated by extracellular microbial antigen?

MHC-II

What is the adaptive immune response initiated by extracellular microbial antigens?

Antibody Production

What microbe molecules are processed for presentation when initiated by intracellular microbial antigens made antigen made inside host infected cells?

Proteins

What fragments are presented when initiated by intracellular microbial antigens mafe inside host infected cells?

Peptides

What cells present the antigen when initiated by intracellular microbial antigens made inside host infected cells?

Any host infected cell with a nucleus

What cells respond to the presented antigen when initiated by intracellular microbial antigens made inside host infected cells?

CTLs

What MHC molecule is used to present the antigen when initiated by intracellular microbial antigens made inside host infected cells?

MHC-I

What is the adaptive immune response result when initiated by intracellular microbial antigens made inside host infected cells?

Activated CTLs (Cell-mediated Immunity)

What type of adaptive immunity is observed with almost any natural exposure to a pathogen or with a vaccine?

Both humoral and Cell-Mediated one usually dominated the other.

How can microbial antigens that are made inside host cells end up inside the pro/semi-pro APC and presented to T-helper cells to make cytokines?

Microbe-infected host cells will be killed at some point, the microbial antigens will be released in the extracellular space which can be engulfed by APC.

How can microbial antigen outside of cells get presented to CTLs and generate a Cell-mediated immune response?

Dendritic cells and Macrophages can engulf antigens outside of cells and present to CTLs since the also have a nucleus so they will also have a MHC-I receptor so it activate both pathways.

A host cell becomes infected with a virus what innate response will be activated?

NK cells kill host cell and viral proteins enter the extracellular space

What can the adaptive immune system do in the response to this infection?

Virally infected Host cells processed present viral peptides to CTLs. Activated CTLs can kill infected host cells.

How do B-cells play a role in the vial infection during a adaptive immune response?

B-cells with BCR specific for viral proteins can internalize proteins process them and present them to T-Helper cells get cytokines to make the B-cells into plasma cells to make specific antibody against the virus.

What can an antibody do against a virus/antigen?

Neutralize virus

Opsonin

Compliment activation

Form antigen-antibody complexes that are engulfed by macrophages

A dog becomes infected with an extracellular bacteria, what can the innate immune system so in response to this infection?

Phagocytosis by Neutrophils and Macrophages: using PRC for PAMPs on the microbe

Activate the Alternative complement pathway to generate opsonins (C3b) and generate the MAC

What are the two main types of T-helper cells?

Th-1

Th-2

What cytokines do Th-1 make?

Interferon gamma (IFN-g)

Interleukin 2(IL-2)

What does Th-1 usually cytokines promote?

Cell-mediated immunity

What are the cytokines that Th-2 produce?

IL-4

IL-5

What does the Th-2 cytokines usually promote?

Humeral Immunity

If there are no vaccines for a pathogen what does this mean for the adaptive immunity?

If there is no vaccine that means that adaptive immunity struggles against it

What is the innate immune response to protozoa?

Innate response are similar to those for bacteria and viruses reflecting whether its in the intra or extracellular

What is the adaptive immune responses to protozoa?

Protozoa stimulate both antibody and cell-mediated:

• Antibody and Complement target extracellular stages along with phagocytic cells

  • Th-1 cytokines activate CTLs and macrophages can target intracellular stages along with NK cells

Once an intracellular protozoa gains entrance to a host cell what adaptive immune response will respond?

A Th-1 cytokine response and good cell-mediated immunity is most effective. (CTLs and Macrophages)

Why are helminths a challenge for the immune system?

Large size

Complex nature

Good at avoiding immune mechanisms

Why type of receptor do helminths express?

PAMPS and release antigenic molecules

APC present helminth antigens to which T-Helper cells and to make what antibody?

Th-2

Generate Mainly IgE antibody

Intestinal mucosa are rich in what type of cells?

Mast cells

Parasite-specific IgE binds to to mast cells what region of the antibody does the antigen have to bind?

Fab

What happens to the mast cells once the parasite-specific antigen binds to the Fab region of the IgE antibody?

Mast cells degranulate

What does the mast cell degranulation result in?

Vasodilation

Tissue edema

Recruitment of Eosinophils

What can be observed with a helminth infection?

An increase in numbers of eosinophils in the blood (eosinophilia)

What do Eosinophils release?

pro-inflammatory molecules

What does the pro-inflammatory cause the helminth to do and how does it effect the GIT?

It causes the helminth to detach and causes an increase in peristalsis to help expel the helminth

What are the two antibodies that coat the helminth?

IgE and IgG

How do IgE and IgG fight a helminth in the tissues?

IgG and IgE release a substance toxic to the helminth while macrophages wall off and destroy the Helminth.

How does a fungal pathogen provide a challenge for the immune system?

Large colony size hard for the immune system to control

Where does fungi usually breach the body?

innate barriers of the respiratory mucosa (epithelium, mucosa)

If phagocytic cells can phagocytize fungi elements, why can’t it not effectively kill them?

Hyphae are too large for phagocytic cells to target and destroy effectively.

What type of inflammation is usually seen in innate response to a fungal infection?

Acute inflammation

If dendritic cell and macrophages cannot kill the fungal infections what do they do to fight it?

Engulf fungal elements to present fungal antigens to T-helper cells

How does the adaptive immune response respond to a fungal infection?

APC present fungal antigens to Th-1 cells to product IFN-y cytokine to enhance the macrophage function. This often causes granulomatous inflammation, some antibody production will also occur that may facilitate phagocytosis and NK cell function (ADCC)

Infection with what type of pathogen is most likely to be associated with an eosinophilia?

Helminth

When a host is exposed to rabies virus, the virus initially remains outside of host cells for at least a few days before infecting nerve cells. What adaptive immune mechanism is most effective prior to the virus infecting nerve cells?

Antibody

What is essential for the establishment of chronic or latent infections?

Immune evasion

What are general strategies for viral immune evasion?

Sabotage cytokine and chemokine communication

Disruption of NK cells and CM defense mechanism

Subversion of MHC antigen processing and presentation

Escape form humoral immunity by antigenic drift/shift

Interference with complement cascade

Short-circuiting programmed cell death pathways

Why are fungi so good at evading the immune system?

Outer cell wall polysaccharides inhibit immune cells

What are the mechanism of parasite immune evasion?

Hiding of parasite

Location in the lumen of the GI or respiratory system (not able to fight well)

Migration to a new site

Antigen modification (mimic antigens that look like the host)

Inhibition of immune factors

How does a parasite evade the immune system by fighting inflammatory cells?

They produce anti-flammatory mechanism

How does a parasite evade the immune system by fighting the CTLs?

They block antibodies

Immunosuppression

How does a parasite evade the immune system by fighting B-cells?

Masking antigens

Mimicry

antigenic variation