4.1.6(Specific immune responses)

State the name of the process of activating B and T lymphocytes

• Clonal selection

What are B memory cells

• Cells that remain in the blood for a long time, providing long-term immunity

What is meant by clonal expansion

• An increase in the number of cells by mitotic cell division

What is meant by interleukins

• Interleukins are signalling molecules that are used to communicate between different white blood cells to activate an immune response

What are plasma cells

• Derived from B lymphocytes, these are cells that manufacture antibodies

State the 4 types of T lymphocytes

• T helper cells(Th)

• T Killer cells(Tk)

• T memory cells(Tm)

• T regulatory cells(Tr)

Describe where T and B lymphocytes are made and where they mature

• T lymphocytes are made in bone marrow but mature in the thymus

• B lymphocytes are made in bone marrow and mature in the bone marrow aswell

Describe the process of activating T helper cells

• Pathogens are phagocytosed by macrophages and display the invading antigen on the outside of the cell to become a antigen presenting cell(APC)

• APCs travel to the nearest lymph node to present information about the captured pathogen to the many T helper cells

• When a T helper cell recognises an antigen on the APC, as it has a complementary receptor, it binds to it and becomes activated

Describe what happens after T helper cells are activated

• These T helper cells release interleukins:

  • These stimulate the activation of B lymphocytes and T killer cells

  • They also stimulate Phagocytosis by phagocytes

• Once the correct T helper cell is selected(clonal selection) and activated, they start replicating by mitosis on a large scale - Clonal expansion

Describe how T killer cells are activated

• They are activated when receptors on their surface detect foreign antigens on the surface of the pathogen

• They are further stimulated by the release of interleukins

Describe what happens after T killer cells are activated

• They under go clonal selection and clonal expansion by mitosis

• They then attack and kill infected cells and cancer cells

Describe the role of T regulatory cells

• They shut down the immune response after the pathogen has been successfully killed and removed from the body

• They prevent the body’s lymphocytes from attacking the body’s own cells

• They supress the immune response of other which blood cells

Describe the process of activating B lymphocytes

• Antibodies on the B lymphocytes are complementary to the antigens on the pathogen cells. The B lymphocytes bind to the pathogens

• They then internalise the pathogens and process them and present receptors on the surface of the B cells to become antigen presenting cells(APCs)
  The presented antigen is then recognised by T helper cells specific to the receptor

• This causes The T helper cells to produce interleukins which causes the activation of B lymphocytes is clonal selection

• The B lymphocytes then undergo clonal expansion by mitosis

Describe what happens to B lymphocytes after clonal expansion

• They divide by mitosis during clonal expansion to product genetic clones of its self

• During this process, 2 new types of cells are created:

  • Plasma cells

  • B memory cells

Describe the role of plasma cells

• They manufacture and produce and secret loads of antibodies specific to the antigen, so these antibodies attach to antigens on the pathogen and destroy them

Describe the role B and T memory cells

• After being exposed to the antigen, B and T memory cells are produced

• These memory cells remain in the body for a long time to provide immunity

Describe how T memory cells and B memory cells are different

• T memory cells: Receptors recognise specific antigens and respond quickly

• B memory cells: Lots of memory cells have specific anti bodies on their surface with complementary shape to the antigen, Response of B memory cells is quicker than T memory cells