12. Communicable diseases

specific and non specific

response is the same for all pathogens eg. physical and chemical barriers, phagocytosis

response is specific to each pathogen eg, cellular response and humoral response

• determines specific immune response • type of white blood cell • produced in bone marrow

• mature in thymus gland • involved in cellular response where they respond to antigens presented on body cells

T and B lymphocytes/cells

• mature in bone marrow • involved in humoral response where they produce antibodies found in body fluids

T: helper, killer, regulator and memory cells

• have receptors on their cell-surface that bind to complementary antigens on antigen-presenting cells • produce interleukins (type of cytokine) which stimulate B cells or phagocytes • can form memory or T killer cells

• kills abnormal and foreign cells by producing a protein • this protein makes holes in the cell-surface membrane, causing it to become freely permeable and causing cell death

• suppress immune system after pathogens have been destroyed • this helps prevent the immune system from mistakenly attacking body cells

• provide long-term immunity against specific pathogens • provide rapid response if the body is re-infected by the same pathogens

• macrophages engulf pathogens and display their antigens on the cell-surface. they are now known as antigen-presenting cells • T helper cells with complementary receptors bind to these antigens • on binding, T helper cell is activated to divide by mitosis to form genetically identical clones

develop into memory cells - circulate in body to provide long term immunity develop into T killer cells - destroy infected cells stimulate phagocytes - cells produce interleukins which stimulate phagocytoses to engulf pathogegns stimulate division of B cells - cells produce interleukins, which stimulate B cells to divide and produce antibodies

leaf drops off

set up extra mechanical defences and produce callose - a polysaccharide containing B1-3 and B1-6 bonds between glucose monomers

• structured differently • more flexible and easier to build and break down quickly

• around sieve plates

• regulates flow of sap through sieve tubes • can block sieve plates when needed

• if a plant is damaged (eg attacked), callose is rapidly deposited • this seals off the sieve tubes, preventing loss of sugars and protecting the plant

a type of non-specific defence involving a type of cell known as a phagocyte

type of white blood cell that engulf and destroy pathogens (phagocytosis) found in blood and body tissues of many organisms

neutrophils - rapidly engulf and destory pathogens at site of infection macrophages - engulf and digest pathogens but also present pathogens antigens on its cell surface to activate other cells in immune system

molecules that help with process of phagocytosis