IMMUNE RESPONSE OF PLANTS AND ANIMALS

• Immunity is an organisms ability to resist disease

• Living organisms have evolved many defence mechanisms against disease

• Plants & animals are under threat of infection by viruses, bacteria and fungi

• It’s the task of the immune system to keep the microbes out of the body,

or if they do enter, find them and destroy them

IMMUNITY IN PLANTS Do Not Have An Immune System

PREVENTION: Use of passive mechanisms

• Waxy cuticle

• Bark

• Lignin

• Suberin

• Irritating and poisonous sap

CARE OF WOUND: Use of chemicals

• Resin and gum – antiseptic

• Bioflavonoids (anti-bacterial and anti-viral)

• Prevent the entrance of pathogens into their tissues

• Resistance to fungal infections

• Salicylic acid (plant hormone) – cell death of infected tissues prevents spread of pathogen

• Also activates responses elsewhere in the plant

IMMUNITY IN ANIMALS

• Animals have an internal immune system known as natural immunity

• Consists of the skin, lymph system, spleen and bone marrow

• It manufactures leucocytes (WBC) that destroy pathogens

• Two types: lymphocytes (B & T) and phagocytes

IMMUNITY IN ANIMALS

• Acquired Immunity (specific)• Specific immunity provides protection

against specific pathogens

• When a pathogen invades the body there is an immediate, non-specific response while the specific immunity is kick-started

• White blood cells called lymphocytes

• B and T cells (lymphocytes)

• Acts against specific pathogens by recognising the antigen and “remembers” them

• Antigens activate the immune response and interact with the cells of the immune system

• Next time it encounters that pathogen the response will be a lot quicker

• Innate Immunity (non-specific)• Physical barriers such as skin or

mucous membrane

• Chemical barriers such as tears or hydrochloric acid in the gut

• Phagocytic cells that engulf foreign matter (macrophages)

• Inflammation which attracts macrophages • When mast cells are damaged they

release histamine

• Blood flow increases (red and warm)

• Blood vessels “leak” causing swelling

• Genetic barriers (host specific)

ACQUIRED IMMUNITY

• Protects us against infectious diseases

• Specific reaction against specific pathogen and eradicates it from the body

• This is how immunity develops

• Can deliberately expose yourself to pathogens to build up immunity (vaccines)

• Two types of immunity:

• Cell-mediated immunity

• Antibody-mediated immunity

• Activity 29 on pg 72

WAYS OF ACQUIRING IMMUNITY

LYMPHATIC SYSTEM

• Consists of lymph vessels that pass through lymph nodes

• Lymph nodes is a fibre network with lymphocytes that filters lymph

• Tonsils protect against bacteria and pathogens that enter through mouth and nose

• Spleen does not filter lymph but identifies and destroys bacteria and old RBC

• Thymus gland is where lymphocytes mature and differentiate to fight specific

pathogens

• Undifferentiated lymphocytes released from bone marrow and circulate the body,

Some reach the thymus gland where the differentiate to form T-cells. The others are

known as B-cells.• T and B cells accumulate in different parts of the body such as lymph nodes and

spleen

• They have receptors on their cells to recognise specific antigens

CELL-MEDIATED IMMUNITY

• T-cells:

• T-helper cells (CD4T cells)

• Cytotoxic T cells• Killer T-cells

• CD4T cells are targeted by the HIV

• They stimulate B-cells for the production of antibodies

CELL-MEDIATED IMMUNITY

ANTIBODY-MEDIATED IMMUNITY

• Antibody is a “Y” shape and the top part varies

• The variable part means it can bind with different antigens

• Antibodies are found in body fluids (blood plasma, tissue fluid, lymph)

• B-cells come into contact with an antigen on a pathogen

• B-cells have specific receptors on their surfaces

• Two types of B-cells:

• Plasma cells that secrete large amounts of the antibody into the blood and

lymph

• B-memory cells which live 20-30 years

Summary of the specific immune response on page 77, Figure1.1.55

TYPES OF IMMUNITY

• Active immunity: exposure to pathogens through natural infections or

vaccines. Stimulates immune response either with or without disease symptoms

• Passive immunity: when antibodies are passed to a baby through the

placenta or breastmilk, or injection with antibodies (short term immunity

without an immune response)

VACCINESEFFECTIVE MEANS OF STIMULATING ACTIVE IMMUNITY

• A vaccine is made from a weakened or dead strain of a pathogen

• When the vaccine is administered the body responds by making antibodies against the pathogen

• The antibodies destroy the pathogen

• When the body is exposed to the pathogen later antibodies already exist and the lymphocytes recognize the pathogen quickly and destroy them before the person becomes sick

VACCINES• The use of vaccines has completely

eradicated smallpox and almost completely eradicated polio

• All South Africans should be vaccinated against the following diseases

• Hepatitis (viral)• Diphtheria, tetanus and whooping cough

(bacterial)• Haemophilus influenza (viral)• Polio (viral)• Measles, mumps and rubella (viral)• Chickenpox (viral)

• Some vaccines require boosters

• Individuals are protected through herd immunity (disease can’t spread)

• Activity 31 page 80

ANTIBIOTICSANTI-VIRAL AND ANTI-MICROBIAL DRUGS

• Antibiotics CANNOT treat a viral infection but may be used for treatment of bacteria, Protista and fungi

• Antibiotics either:

• Kill bacteria (bactericidal)

• Slow down/stop growth (bacteriostatic)

• Antiretroviral drugs are used to control HIV

TRADITIONAL BIOTECHNOLOGY

• Alcoholic drinks (wine, beer) are made using alcoholic fermentation

• Yeast uses fermentation to produce ethanol (alcohol) and carbon dioxide (fizz)

• In Southern Africa beers have been made via fermentation for centuries using sorghum, maize or cassava

• Other products that are made using fermentation are fermented milk (Amasi) and cheese

• Pg 83-84