IMMUNITY ABBOTTS 2010

INFECTIONS DEFINITION Are caused by pathogenic Monera [viruses and bacteria] and Protista [Protozoans] and Fungi An infection is the detrimental colonization of a host organism by a foreign species.

PATHOGENS = disease causing micro-organisms bacteria virus fungi, protozoa,

IMMUNE RESPONSE BY PLANTS Plant pathogens harm plant growth and reproduction Plants have an immune system to defend themselves against infections A plant recognizes the shape of the infecting pathogen and the infected cells are stimulated

IMMUNE RESPONSE IN PLANTS Produce salicylic acid a plant hormone or signal It is an asprin-like compound Activate resistance genes which resist the pathogen – e.g. stop viral replication Self destruct – form an area of dead cells to prevent the infection from spreading

SYSTEMATIC ACQUIRED RESISTANCE Salicylic acid moves from the infected site through the phloem to uninfected parts of the plant to activate the immune system to produce defensive compounds to make the entire plant resistant to the pathogen

FIRST LINES OF DEFENCE tears antibacterial enzymes Try to prevent the entry of germs tears antibacterial enzymes saliva antibacterial enzymes mucus linings traps dirt and microbes skin prevents entry stomach acid low pH kills harmful microbes “good” gut bacteria out compete bad

PATHOGENS = disease causing micro-organisms bacteria virus fungi, protozoa,

SECOND LINES OF DEFENCE IF GERMS DO GET INTO THE BODY: Primary response – tries to destroy the germs and prevent them from spreading Secondary response – if germs do spread, the immune system is activated

PRIMARY RESPONSE Tries to destroy the germs and prevent them from spreading by: Inflammation (if it is a local infection) Fever (raised body temperature)

INFLAMMATION Local infection Inflammation is a process by which the bodies white blood cells protect us from infection and foreign substances such as bacteria and viruses

SECONDARY RESPONSE/SPECIFIC RESPONSE If germs do start to spread Immune system becomes involved

IMMUNITY The body’s active response to an infection

THE IMMUNE RESPONSE INVOLVES TWO MAIN MEASURES: Destruction of the invading germs Holding a memory of this response

TWO GROUPS OF WHITE BLOOD CELLS INVOLVED IN THE IMMUNE RESPONSE LYMPHOCYTES B LYMPHOCYTES T LYMPHOCYTES PHAGOCYTES They are part of a huge army in our bodies There are about one trillion B lymphocytes And one trillion T lymphocytes They are found in the tonsils, lymph glands, spleen and blood

ANTIGENS all cells have surface markers called antigens. body can recognise these as self or non-self (foreign)

B LYMPHOCYTES Also called antibody cells If a germ gets into the body, it is detected by these cells

HOW B LYMPHOCYTES DESTROY GERMS Germs have molecules called antigens on their surface The antigen tells the B lymphocyte that the germ is ‘non-human’ and dangerous There are countless types of B lymphocytes Each is able to recognize its own specific antigen The B lymphocyte replicates rapidly producing lots of identical cells (clones) These newly formed B lymphocytes produce proteins called antibodies into the blood plasma

The antibodies combine with the antigens on the surface of the germ BINDING OF ANTIBODIES AND ANTIGENS This will destroy or neutralise the germ Some of the B lymphocytes stay in the lymph glands as memory cells If they encounter the antigen again, they mount a response very quickly and kill the germ before it can breed This is the basis of immunity

HOW ANTIBODIES DESTROY GERMS DIAGRAM: METHODS OF GERM DESTRUCTION BY ANTIBODIES Antibodies could: Cause bacterial cells to burst Label germs for phagocytosis Cause germs to clump together [clumps are easier to ingest by phagocytosis] Neutralize bacterial toxins

T LYMPHOCYTES There are different types of T lymphocytes Each cell has a unique role to play in the immune response CD4 Cells [helper T cells] Killer T cells  Killer T cells CD4 cells are a type of white blood cell (lymphocyte

CD4 CELLS/ HELPER T CELLS Begin the immune response to infections Without these cells the other cells will not do anything Body’s ability to fight infections would be very poor

KILLER T CELLS/ CYTOTOXIC T CELLS They attack and destroy: Cancer cells Cells infected with viruses and some parasites Transplanted organs [unless immunosuppressive drugs are given to the patient]

PHAGOCYTES (CELLS THAT EAT!) DIAGRAM: Are large lymphocytes (white blood corpuscles) Can change shape They engulf germs by phagocytosis [and also dead cells and foreign particles]

HOW DO PHAGOCYTES DESTROY GERMS Move around the body looking for germs Squeeze through gaps in capillary walls and reach any part of the body When it comes into contact with a germ, it engulfs it and takes the germ into the cell Germ is digested and killed Process called phagocytosis

Phagocytosis of E coli

DEALING WITH INFECTIONS

THE END