Chapter 11 Immunity in Humans PDF

ALIA NAZIRA – IMMUNITY ↘ Immunity is the body’s ability to PATHOGENS fight infections caused by pathogens ❑ Th...

ALIA NAZIRA – IMMUNITY ↘ Immunity is the body’s ability to PATHOGENS fight infections caused by pathogens ❑ The body defence system reacts when or other foreign objects, though pathogens infect the body specific attacks on the pathogens ❑ A pathogen is microorganism that ↘ When our body can fight a disease, causes diseases we are said to be immune to that ❑ Examples of pathogens disease 1 Bacteria (singular: bacterium) ↘ There are three lines of defence to 2 Viruses fight against diseases in our body 3 Parasites a. The first line of defence ❑ Pathogens can only cause diseases if b. The second line of defence they successfully infect body cells c. The third line of defence ANTIGENS The first line of  The body defence system recognises pathogens as foreign particles known as antigens defence  Antigens are foreign particles that  The first line of defence consists of enter the body and subsequently the physical and chemical line-up stimulate the immune response that prevent pathogens from entering the body ANTIBODIES  The first line of defence is the ◊ Antigens stimulate the lymphocytes defence line that is not specific and to produce antibodies into the blood acts to prevent pathogens from flow to destroy the antigens entering the body ◊ Antibodies are protein found on the LYSOZYME lymphocyte surface or proteins released by lymphocytes into the ∆ Lysozyme is an antimicrobial protein blood plasm that can dissolve and destroy some types of bacteria IMMUNE RESPONSE ∆ Lysozyme found in → The interaction between antibodies 1. Tears and antigens that cause antigens to 2. Nasal mucus be destroyed is called the immune 3. Saliva response 1 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA MUCOUS MEMBRANE ⌂ The mucous membrane that lines the The second line of respiratory tract secretes a sticky fluid called mucus defence ⌂ Mucus contains lysozyme that ○ The second line of defence is destroys bacteria found in the air 1) Fever that enters the respiratory system 2) Phagocytosis MECHANISM OF BLOOD CLOTTING 3) Inflammation ○ The mechanism of the second line of » The blood clotting mechanism defence is also not specific prevents bacteria from entering through wounds FEVER HYDROCHLORIC ACID Fever is the second line of defence mechanism that fights infections ꚛ Hydrochloric acid in the stomach Fever increases phagocytic activity destroys bacteria present in food and fights against microorganisms and drinks that infect the body SKIN PHAGOCYTOSIS  It is the physical defence that ❖ The phagocyte is a leucocyte that prevents the entry of pathogens can carry out phagocytosis because it is though and is difficult ❖ Neutrophils and monocytes are for microorganisms to penetrate phagocytes  The continuous shedding of dead cell ❖ Phagocytosis is the process by which layers on the skin surface makes it microorganisms or other particles difficult for various types of such as dead cells are trapped and microorganism to grow digested by phagocytes  Acts as a chemical shield through the ❖ When an infection occurs, the secretion of sebum phagocytes move the infected area  Oil and acid in the sebum prevent the and enter the tissue fluid through growth of various types of the pores of the capillary wall microorganisms ❖ When a phagocyte encounters a  Sweat secreted by the skin contains pathogen, the phagocyte will engulf lysozyme, a type of enzyme that the pathogen and the lysozyme in the breaks down the cell wall of some phagocyte will digest the pathogen bacteria 2 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA INFLAMMATION ▪ Inflammation is the immediate response that destroys and neutralises harmful actions of microorganisms and toxins at the early stages of infection 3 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA The third line of to destroy the antigens and foreign particles This will cause the lymph defence » nodes to swell » The lymph nodes also contain ◊ If pathogens overcome the second macrophages that destroy line of defence, the third line of bacteria, dead tissues and defence will be activated foreign particles through ◊ The third line of defence is the phagocytosis immune response of the lymphocytes » Lymphocytes are divided into » The lymphocytes formed in the two types, lymph nodes produce a) T lymphocytes antibodies Attacks cells infected » The actions of antibodies are by pathogens specific b) B lymphocytes » Each type of antibody can T lymphocytes only combine with a certain stimulate B type of antigen lymphocytes to produce » When a person is infected memory cells with pathogens, a large » If the same pathogens number of lymphocytes will attacks, the memory cells will accumulate in the lymph nodes be stimulated to produce antibodies immediately 4 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA 5 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA – NEUTRALISATION  Antibodies bind with toxins produced AGGLUTINATION by bacteria and neutralise the toxin Antibodies coagulate the pathogens and make them an easy target to be trapped and destroyed by phagocytes OPSONISATION » Antibodies combine with antigens and act as a marker for phagocytes to PRECIPITATION recognise the antigens and destroy them ◊ Antibodies react with dissolved antigens to form an insoluble complex (precipitate) that is easily destroyed by phagocytes 6 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA LYSIS → Antibodies combine with antigens and cause bacteria to be broken down and decomposed 7 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA – permanent immunity against the disease ↘ There are two types of immunity  When the individual is attacked again ◊ Active immunity by the same pathogen, the Lymphocytes produce their lymphocytes that stored memories of own antibodies as a response the pathogen (memory cells) will to stimulation by the antigens rapidly produce antibodies to react ◊ Passive immunity immediately against the antigens The body receives antibodies ARTIFICIAL ACTIVE IMMUNITY from an external source ∆ To protect oneself from being ↘ Both of these types of immunities infected by a highly infectious can be naturally or artificially disease, an individual can be acquired immunised against the disease Active Immunity ∆ Immunisation refers to the process that stimulates immunity against a specific disease through vaccine ⌂ Antibodies are produced naturally by injections lymphocytes ∆ Vaccine is a suspension of pathogens ⌂ Active immunity remains for a long that are weakened, dead or non- period of time virulent ⌂ There are two types of active ∆ When a vaccine is injected into the immunity body, the vaccine will stimulate a. Natural active immunity lymphocytes to produce antibodies Acquired after an individual to fight the pathogens recovers from an infection ∆ The first vaccine injection will b. Artificial active immunity usually result in a low level of Acquired when an individual is antibody production which is given a vaccine injection insufficient to protect an individual NATURAL ACTIVE IMMUNITY from the disease ∆ A booster dose must be administered  When someone is infected by to increase the antibody production pathogens, lymphocytes will produce to a level of immunity that can antibodies as a response to these protect the individual from the antigens disease  When the individual recovers from an ∆ If the individual is infected by actual infection, that individual will gain a pathogens, the lymphocytes will 8 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA produce enough antibodies and NATURAL PASSIVE IMMUNITY immediately destroy these pathogens ꚛ This immunity is acquired by a foetus ∆ Examples: when the mother’s antibodies diffuse 1. Salk for poliomyelitis through the placenta into the blood 2. BCG (Bacilli Calmette-Guerin) flow of the foetus for tuberculosis (TB) ꚛ Antibodies also protect the baby for 3. HPV for cervical cancer the first few months after birth Passive Immunity through antibodies that are found in the mother’s milk or colostrum when breastfeeding The body does not produce its own antibodies ARTIFICIAL PASSIVE IMMUNITY Antibodies are obtained from an ◊ This immunity is acquired through an external source antiserum injection or serum that Passive immunity does not persist and contains specific antibodies to fight can only give immediate, short-term specific antigens and temporary protection ◊ The antiserum injection gives There are two types of passive immediate protection but only for a immunity short period of time 1) Natural passive immunity ◊ Examples of antiserum Acquired through i. Antitetanus breastfeeding and from the ii. Anti-rabies and mother to the foetus during iii. Antiserum for poisonous pregnancy snakes 2) Artificial passive immunity Acquired through an antiserum injection 9 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA SIMILARITIES SIMILARITIES o Protects the body from infectious diseases o Involves interaction between antibodies and antigens DIFFERENCES ASPECT ARTIFICIAL ACTIVE IMMUNITY ARTIFICIAL PASSIVE IMMUNITY Acquired Vaccine injection Antiserum injection through Injected Vaccine is a suspension of pathogens Antiserum is a serum that contains substance that are weakened, dead or non- specific antibodies virulent Purpose Prevention Treatment or when immediate protection is required Effect Does not give immediate protection Gives immediate protection Immunity Immunity lasts for a long period of Immunity is temporary and does not period time persist When injection Vaccine injection is administered Antibody injection is given in is given before being infected advance if there is a high risk of infection or immediately after being infected by a disease Antibody Antibodies are produced by the Antibodies are obtained from lymphocytes antiserums The need to Must be given to boost the level of Is only given when the antibody level give a second antibodies above the level of in the blood drops below the level of injection immunity as a protection against the immunity and the patient is still (booster disease infected by the disease dose) 10 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA – HIV TRANSMISSION ↘ HIV enters the body through the transfer of body fluids such as blood and semen or across the placenta HUMAN IMMUNODEFICIENCY VIRUS (HIV) ↘ Women infected with HIV can » Human Immunodeficiency Virus (HIV) transfer the virus to the baby during is a virus that attacks the human pregnancy, birth or breastfeeding immune system ↘ Nevertheless, HIV infection in the » HIV infection causes Acquired foetus and new born baby can be Immunodeficiency Syndrome (AIDS) avoided with proper medical » An AIDS patient is easily infected by treatment when the mother is other diseases because of the pregnant and during birth progressive destruction of the ↘ Individuals can be infected by HIV individual’s immune system through when they share » HIV spreads in the lymphocyte and contaminated needless used to inject destroys the lymphocyte drugs or tattoo ink ↘ In addition, HIV is also spread ACQUIRED IMMUNODEFICIENCY SYNDROME through HIV-infected blood (AIDS) transfusion ❑ An individual infected with HIV does not show any symptoms for the first few years although HIV has been actively attacking the immune system ❑ Symptoms of the disease include chronic diarrhoea and fungi infection which are only visible after 8 to 10 years ❑ Since the immune system of the individual is already weakened, the body can be easily infected by diseases ❑ Finally, the immune system is paralysed and the patient will die from other infections 11 |CHAPTER 11 – IMMUNITY IN HUMANS ALIA NAZIRA 12 |CHAPTER 11 – IMMUNITY IN HUMANS