Adaptive immune system

How is the helper T cell activated?

• interacts with B cell when it sees its antigen

• interacts with APC that displays an antigen

How does the helper T cell respond?

• amplifies antibody production

• activates CD8 T-cell to become cytotoxic and kill target cells

How is the cytotoxic T cell activated?

identifies MHC I with recognized antigen

How does the cytotoxic T cell respond?

• inserts perforins

• secretes granzymes into cell membrane to trigger apoptosis

How is the regulatory t cell activated?

dampens immune response to some antigens

How does the regulatory t cell respond?

• prevents autoimmune activation

• releases inhibitory cytokines to dampen immune response

How is a memory cell activated?

either a T or B cell previously saw an antigen or learned about it

How does memory cells respond?

• Memory T - induces proliferation and activates T cells

• Memory B - induces proliferation and activates B cells

How is the B cell activated?

recognizes antigen

How do B cells respond?

differentiates plasma cell to make antibodies

How are plasma cells activated?

after antigen recognition and B cell differentiation

How do plasma cells respond?

generates antibodies against specific antigens

How are the APCs (antigen-presenting cell) activated?

presents antigens to T cells so they can learn

How does the APCs respond?

educates T cell

What is an antigen?

protein fragment that is used to develop memory or recognized for an immune response

What is an antibody?

immunoglobin protein that recognizes a specific antigen

What is immunogenicity?

ability to induce immune cell proliferation

What is reactivity?

ability of lymphocytes and antibodies to recognize or attack an antigen

What is a MHC protein?

major histocompatibility protein

What is the MHC class I protein?

self cell that presents foreign antigen

What is the MHC class II protein?

APC showing a T-cell the antigen to learn about

How are antigens and antibodies are related to each other?

antibodies bind to antigens and that leads to them becoming a target for destruction via the complement pathway via phagocytosis

What is humoral immunity?

antibodies and B cells in the humors (fluid) in the body

does not attack cells but marks target

What is cellular immunity?

attacks foreign pathogens and cancer cells

complete antigens are

immunogenic and reactive

hapten antigens are

only reactive

What are the structures of antibodies?

2 heavy chains and 2 light chains

constant regions

variable regions

What are IgM antibodies responsible for?

primary response

What are IgM antibodies secreted by?

plasma cells

What are IgG antibodies responsible for?

secondary response and late primary

What is IgA responsible for?

stopping pathogens from attaching to epithelial surfaces

What is the IgD responsible for?

• doesn’t circulates

• educates B cells

• increases antibody production

Where are IgD antibodies located?

on the B cell

What are IgE antibodies responsible for?

triggers histamine and leads to inflammation

What do IgE antibodies bind to?

mast cells or basophils

How do lymphocytes develop, mature, and activate?

1. red blood marrow

2. immunocompetence and self-tolerance is developed

3. seeding lymphocytes - t cell circulate

4. antigen encounter and activation

5. proliferation and differentiation - effector cells and memory cells

What is immunocompetence?

learning to recognize one specific antigen

What is self-tolerance?

must not recognize any self antigens

What are the adaptive defense characteristics?

specific immunity, systemic immunity, and immunity memory

What is specific immunity?

targeting specific antigens and variants

What is systemic immunity?

antibodies move through lymph

What is immunity memory?

storing knowledge of past viruses so response next time to same virus is more efficient

What shape are IgG, IgD, and IgE?

y shaped (monomer)

What is this?

IgM antibody and it’s a pentamer

What is this?

IgA antibody and it’s a diamer

How many antigens can bind to a monomer shaped antibody?

2

How many antigens can bind to a diamer antibody?

4

How many antigens can bind to a pentamer?

5

How does immunological memory work?

First, a person’s body has to be exposed to a new pathogen. In the primary response, new plasma cells are being made, but memory cells are also being made. If the pathogen enters the immune system again, the immune system will be able to respond faster and produce antibodies at a faster rate.

What is an example of naturally acquired active immunity?

coming into contact with a pathogen

What is an example of an artificially acquired active immunity?

vaccine

What is an example of a naturally acquired passive immunity?

antibodies passed from the mother when the child is in the womb

What is an example of an artificially acquired passive immunity?

injection of someone else’s antibodies

How are b cell activated?

1. antigen binds to B cell

2. activates b cells to proliferate into plasma cells and memory cells

3. IgM antibodies are secreted by plasma if it is a primary response

How is the b cell differentiated?

1. memory cells are activated

2. more plasma cells and some memory cells are immediately made

3. secretes IgG antibodies

Where are IgA antibodies found?

body secretions such as saliva, sweat, intestinal juice, and milk

Where do the T cells mature?

thymus

Where do the B cell mature?

red blood marrow

What are MHC proteins?

glycoproteins that are unique to each individual

What are the functions of MHC proteins?

present antigens to T lymphocytes so they can bind to that antigen

prevents your cells from attacking each other

What can MHC protein hold in their deep groove?

peptide, self antigen, and foreign antigen

What do APCs do?

engulf and present those fragments to T cells to MHC II proteins

What are APCs?

dendritic cells, macrophages, and b lymphocytes

What receptors are on a CD4 cell?

CD4 receptor, T cell receptor, and MHC II receptor

What do CD4 cells differentiate into?

helper T cells and regulatory cells

What receptors do CD8 cells have?

CD8 receptor, T cell receptor, and MHC I receptor

What does CD8 cells differentiate into?

cytotoxic T cells

What are the steps for T cell differentiation?

1. Antigen is presented by APC

2. Double recognition

   1. TCR and CD cell binds to MHC proteins and costimulatory molecule binds

3. CD cell is activated and proliferates to become memory and effector T cells

How are T cells activated?

the CD cell must interact with a MHC protein, a costimulatory molecule, and antigen bound to T cell receptor

What MHC protein is on all cells except erythrocytes?

MHC I

What are antigens called in healthy cells?

endogenous antigens

When MHC I proteins survey and find foreign antigens being secreted from cells it

activates CD8 cells and informs cytotoxic cells

Where are MHC II proteins found?

only on cells that present antigens to CD4 cells

• dendritic cells

• macrophages

• b cells

What stimulates helper t cells?

interleukins

What does the helper t cell do?

enhances lymphocyte functions

How do cytotoxic cells function?

releases perforin to break the target cell membrane and then releases granzymes to induce apoptosis

What occurs when the antigen-antibody complex is formed?

• neutralization

• agglutination

• precipitation

• complement activation

What is neutralization?

antigens and antibodies bind and prevents viruses/bacteria from attaching and infecting host cells

What is precipitation?

antibodies bind to proteins and this results in antigens dissolving

What does the complement activation result in?

enhancement of phagocytosis and inflammation

cell lysis

What does neutralization, agglutination, and precipitation enhance?

phagocytosis

Where do CD4 cells and CD8 cells go before they become effector cells?

lymphoid tissues and organs