Chapter 7 part 2- unit 4 biology

third line of defense

• is initiated by the presentation of non-self antigens to specific immune cells of the adaptive immune system.

• a subset of the immune system within vertebrates that is composed of the humoral and cell-mediated responses which create a specific immune response and form immunological memory

2 features of the adaptive immune system

• specificity – the adaptive immune system responds to each distinct pathogen in a unique and tailored manner

• immunological memory – the adaptive immune system results in the production of cells that allow the body to respond to future re-infections by a previously encountered pathogen quickly and effectively.

lymphatic system functions

• transportation of antigen-presenting cells to secondary lymphoidtissues for antigen recognition and initiation of the adaptiveimmune response​

• production of leukocytes, including lymphocytes (B and T cells) inprimary lymphoid tissues​

• removal of fluid from tissues around the body​

primary and secondary lymphatic organs

• Primary organs are the thymus and bone marrow​

• Secondary organs are lymph nodes, spleen and tonsils​

adaptive immune system traits

• Slower (takes days rather than mins/hours)​

• Specific and has memory​

• Host recognises and responds to specific antigens which thepathogen possess​

• Humoral immunity (B lymphocytes and antibodies)​

• Cell mediated immunity (T lymphocytes)​

• Memory of specific antigens means that subsequent exposure tothem will have a greater and more rapid response​

Antibodies

•  a protein produced by plasma cells during the adaptive immune response that is specific to an antigen and combats pathogens in a variety of ways.released by plasma cells

• are proteins with quaternary structures

• compose of 4 polypeptide chains- 2 heavy chains and 2 light chains

• 2 heavy chains joined together by sisulphide bond

neutralisation

bind to pathogens or toxins, blocking their ability to enter or damage host cells.

agglutination

• the clumping of particles together. In the immune system, antibodies can help clump pathogens together

• Antibodies can bind together with antigens on two separate pathogens, forming large antigen-antibody complexes. This makes it easier for phagocytes to recognise the pathogens as foreign bodies and destroy them.

Immobilisation

Antibodies can also restrict the movement of pathogens around the body through the formation of large antigen antibody complexes.

Opsonisation

Antibodies can bind directly to the surface of a pathogen to make it easier to phagocytose.

activation of complement proteins

Antibodies attached to the surface of pathogens can facilitate the actions of complement proteins, including the formation of membrane attack complexes (MACs).

Ig A

Found in mucus, breast milk, and saliva.

Ig D

Important for the activation of other immune cells.

Ig E

Protects against parasitic worms. Also responsible for allergic reactions.

IgG

Most common antibody found in the body. Able to cross the placenta and travel to the foetus

IgM

The first type of antibody produced by plasma cells in response to an infection.

Antigen presentation

• Engulf APCs engulf and digest pathogens and

• Display the pathogen on the MHC 2 markers

• Travel via nodes to the lymph node

• Bind Antigen binds to the T helper cell with a complementary receptor

• Selection T helper cell becomes activated and is ‘selected’

T helper cells

Supports the functioning of a number of different immune cells, including cloning and differentiation of selected T and B cells

Humoral immunity

• involves the neutralisation and destruction of extracellular pathogens via the production and secretion of antibodies

• an adaptive immune response in which extracellular pathogens are targeted by specific antibodies produced by plasma cells.

humoral immunity steps

• Phagocytosis: The immune response to an extracellular pathogen begins when antigen-presenting cells phagocytose the pathogen. 

• Presentation: These cells then present the antigen to T helper cells in the lymph node, which become activated and release cytokines and bind to stimulate B cells with complimentary binding sites on their antibody to the antigen.  

• Expansion: The selected B cells undergo clonal expansion and differentiate into plasma cells and B memory cells. 

• Antibodies: The plasma cells produce specific antibodies to the antigen (refer to the pathogen if given in question) and are released into the bloodstream, where they help identify and eliminate the pathogen. 

how antibodies and macrophages inhibit spread

• Antibodies bind to bacteria and cause agglutination, macrophages then engulf and destroy them

• Macrophages display foreign antigens of bacteria, the cells stimulate the production of antibodies

role of MHC 2 marker

MHC II allows the cell to present digested foreign antigens on its surface and interact with T and B cells to stimulate the adaptive immune response.

cell mediated death steps

• Presentation: Cell-mediated immunity begins when a pathogenic antigen is presented by an antigen-presenting cell and recognized by a complementary T helper cell

• Cytokines: Once selected, the T helper cell releases cytokines to activate a matching naive T cell with a complementary receptor to the antigen. (colonial selection) 

• Expansion: This T cell undergoes clonal expansion and differentiates into cytotoxic T cells and T memory cells. 

• Destroy: The cytotoxic T cells leave the lymph nodes then target infected cells by binding to infected cells that display the antigen on their MHC1 marker. They then release death ligands that trigger apoptosis. 

B memory cells

rapidly divide and form new antibody producing plasma cells when they encounter an antigen that matches their receptors

T memory cells

multiply rapidly into T helper cells and cytotoxic T cells upon stimulation by an antigen presenting cell that is presenting a previously encountered antigen.

What is B memory cells purpose in providing a long-lasting response to a pathogen?

Once encountering a pathogen at a subsequent time, B memory cells will differentiate into B plasma cells

They will produce antibodies at a faster and greater rate.

Detect antigen on second exposure

Store antibody that is specific to antigen

vaccine

a medical treatment typically containing antigens designed to stimulate a person’s adaptive immune system to create immunity to a pathogen without actually causing disease

primary immune response

the reaction of the adaptive immune system to an antigen it has not previously been exposed to

secondary immune response

the heightened reaction of the adaptive immune system to an antigen it has previously been exposed to

the memory cells created by the first vaccine quickly recognise the antigen in the vaccine and mount a rapid, large secondary immune response. This results in the generation of a large

booster vaccine

a vaccination given to a person later in time after they have completed their initial vaccination program to enhance their existing immunity against a disease.

differences between humoral and cell mediated

Humoral

• Uses B lymphocytes (B cells) that produce antibodies to target pathogens in body fluids (blood, lymph).

• Best at fighting extracellular pathogens (bacteria, toxins, viruses before they enter cells).

Cell mediated

• Uses T lymphocytes (T cells) to directly attack infected cells or coordinate other immune cells.

• Best at fighting intracellular pathogens (viruses inside cells, some bacteria, cancer cells).

T memory cell

can proliferate rapidly into th cells and tc cellswhen the body is exposed to a pathogen for the second time, causing a faster and greater response

B memory cells

Rapidly divide and form new antibody- producing cells