IMMUNITY - CHAPTER 9

What is adaptive immunity

• antigen specific immune response that creates memory for faster future responses

• includes humoral immunity (antibodies) and cellular immunity (T cells)

humoral immunity vs cellular immunity

humoral immunity - molecules found in extracellular fluid and secreted by antibodies, complement proteins

cellular immunity - involves direct attack by immune cells (T cells) against pathogens

what is lymph

Clear fluid similar to plasma,

• returns fluid that seeps from blood vessels+tissues back to circulatory system

• transports lymphocytes and apc’s to lymph nodes

• provides place for lymphocytes. to mature

what are lymph nodes

Structures that filter lymph and have ABUNDANT AMOUNTS OF B and T lymphocytes (apc’s have pathogens that travel to lymph nodes, present antigens to T helper and macrophages (engulf foreign particles, present to T lymphocytes).

• B and T lympho/macros perform inspection + filtering functions

Where do B and T cells mature?

B cells mature in bone marrow

• RESPONSIBLE FOR HUMORAL IMMUNITY

T cells mature in thymus

• RESPONSIBLE FOR CELL MEDIATED IMMUNITY.

lymphatic system and lymphocytes

• composed of lymphatic vessels, similar to circ systems veins, capillaries and lymph nodes

• lymphocytes are specialised cells of immune system. Include T cells, B cells, NK cells.

B cells and T cells

B cells : produced in bone marrow, travel to spleen/other lymphoid organs where maturation occurs.

T cells : produced in bone marrow, travel to thymus where maturation occurs.

primary lymphoid organs and secondary lymphoid organs

primary - Bone marrow and thymus.

secondary - Spleen, lymph nodes, tonsils, adenoids, appendix, Peyer’s patches.

immunity, adaptive and innate

resistance to infectious disease

• adaptive immunity is natural, non specifc, fast and no memory

• innate immunity is aquired, specifc, slow and has ;memory’

antigens (more detail)

• substance capable of inducing immune response in host organism

• epitope is The part of an antigen recognized by antibodies or T/B cells.

• ^specifc part of antigen that antibody binds

cell mediated immunity

helper T cells, Cytotoxic T cells, Memory T cells

helper T cells : cell mediated immunity

• do not directly kill cells

  release cytokines to activate macrophages, B cells, and cytotoxic T cells,

Cytotoxic T cells : cell mediated immunity

Kill infected, cancerous, or foreign cells directly.

Memory T cells :cell mediated immunity

Persist after infection to provide fast responses if re-exposed.

professional apc

1. macrophage takes antigen up by phagocytosis

2. macrophage breaks antigen down into fragments in lysosome

3. class 2 MHC binds an antigen fragment

4. MHC protein present antigen to T helper cell

• if leucocyte engulfs pathogen, it can present antigen attached to class 2 MHC protein

• helper T cells bind to antigens presented this way

• activated helper t cells release cytokines to activate cytotoxic T cells and macrophages to attack infected cells/stimulate b cells to secrete antibodies

T helper cell activation

• professional apc (macrophages, dendritic cells, activated B cells) present antigens on MHC 2 to T helper cells.

Front:
How do helper T (TH) cells get activated?

Back:
APCs present antigens on MHC II to TH cells.
CD4 binds MHC II → activates TH cell.
TH releases cytokines →
• Activates B cells, TC cells, macrophages
• TH cells don’t kill directly.

cell mediated pathway

1. cell infected w bacteria/virus. foreign antigen fragments r created within cells

2. MHC 1 binds antigen fragment

3. MHC protein presents antigen to cytotoxic T cell

• if cell (not wbc) is infected w pathogen, antigens can be taken from pathogen and be presentd to MHC 1

• cytotoxic t cells bind to antigens presented

• cytotoxic t cells recognise cancerous cells

• activated cytotoxic t cells eliminate infected cells directy

cytotoxic t cell activation

Front:
How do cytotoxic T (TC) cells get activated?

Back:
Infected normal cells present antigens on MHC I to TC cells.
CD8 binds MHC I → activates TC cell.
TC cells kill infected cells directly.

Humoral immunity

involves B lymphocytes that produce specific antibodies against non self antigens. After, will release into blood and lymph