Immune system

Question 1

1. What are the main groups of pathogens?

Answer 1

Bacteria, viruses, fungi, protozoa, prions, parasites

Question 2

2. What are some features of bacterial cells?

Answer 2

Prokaryotic, single-celled, cell wall, flagella/ cilia for movement

Question 3

3. What is the difference between primary and secondary hosts of parasites?

Answer 3

The host where the parasite is in its adult and reproductive form is the primary host, the secondary host often holds larval stages.

Question 4

4. What is the difference between endo and ectoparasites and give an example of each.

Answer 4

Endoparasites live internally of a host (eg. Tapeworm), ectoparasites live off the outside of a host (eg. Tick)

Question 5

5. List some features (or absence) common to endoparasites and explain.

Answer 5

Absence of developed gut (live in gut where food already digested), live internally and often in association with partner/ hermaphrodite so no need to locomote, attachment mechanism (to remain in gut), lack of nervous system because live in hostile (acidic) environment.

Question 6

6. What is the definition of disease?

Answer 6

Any condition that detrimentally affects the normal functioning of an organism

Question 7

7. What is the difference between infectious and contagious disease?

Answer 7

Contagious disease requires direct contact with the infected organism, infectious disease the agent (pathogen) can be transmitted through air, water etc.

Question 8

8. Give an example of a protozoan disease.

Answer 8

Plasmodium sp– malaria; cryptosporidium

Question 9

9. What name do we give to a carrier of disease and give an example of a disease transmitted this way.

Answer 9

Vector eg. Mosquito-borne dengue fever, malaria

Question 10

10. How do bacteria cause symptoms of disease?

Answer 10

Toxins that disrupt normal cell functioning, normal immune response (eg. Fever, inflammation)

Question 11

11. Name and describe a bacterial disease.

Answer 11

Cholera – water/ foodborne from contaminated faeces; TB – affects respiratory system, alveoli eaten away and coughed up, fluid-filled lungs; tetanus – produces toxin that affects nervous system, chlamydia

Question 12

12. What is the difference between endo and exotoxins? (notes and SRAM Bacterial Diseases)

Answer 12

Exotoxins are produced by gram-positive bacteria during normal cell growth and metabolism; endotoxins are part of the cell wall of gram-negative bacteria and exert their effect only when bacteria die.

Question 13

13. What is the difference between gram-positive and gram-negative bacteria?

Answer 13

Gram-positive bacteria have larger amount of peptidoglycan and crosslinking of sugars in their cell walls, whereas Gram-negative have a thinner wall and a space between the membrane and cell wall.

Question 14

14. What is the difference between antiseptics, disinfectants and antibiotics? (text p166)

Answer 14

Antiseptics are used on the skin to kill pathogens (70% ethanol kill by breaking down lipids and denaturing proteins; H2O2 kills by oxidation; detergents disrupt cell membranes; iodine binds to proteins), disinfectants are used to kill pathogens on objects (chlorine oxidises; phenols denature proteins; NH4 interact with membranes; CuSO4 precipitates proteins), antibiotics are substances produced by microbes which are active against other microbes.

Question 15

15. How do antibiotics work? (later)

Answer 15

They either kill bacteria directly (bactericidal) or prevent them from growing (bacteriostatic). Some are broad-spectrum and affect a large number of species, others are narrow-spectrum. They interfere with cell walls (penicillin) but penicillin is ineffective against gram-negative bacteria; cell membranes (amphotericin); synthesis of proteins (streptomycin, tetracycline) or nucleic acids (rifampicin). Bacteria need to act inside the host to have any affect so the ideal anti-microbial drug kills the pathogen without damaging the host.

Question 16

Disease

Answer 16

Disease - A particular abnormal condition that negatively affects the structure or function of an organism, and that is not due to any external injury. Diseases are often construed as medical conditions that are associated with specific symptoms and signs. A disease may be caused by external factors such as pathogens or by internal dysfunctions. For example, internal dysfunctions of the immune system can produce a variety of different diseases, including various forms of immunodeficiency, hypersensitivity, allergies and autoimmune disorders.

Question 17

infectious disease

Answer 17

Infectious disease - Infectious diseases are disorders caused by organisms — such as bacteria, viruses, fungi or parasites. Many organisms live in and on our bodies. They’re normally harmless or even helpful, but under certain conditions, some organisms may cause disease. An example of an infectious disease is small pox or flu.

Question 18

non-infectious disease

Answer 18

Non- infectious disease - Diseases that are not contagious are called non-infectious or non-communicable diseases because they can’t be spread from one person to another. So there’s no vector for them to move from one host to another, no virus, no bacteria, no pathogen. Instead, these diseases are caused by other factors, such as genetics, environment, and lifestyle behaviors. Some examples include autoimmune diseasds, cancers, allergies and diabetes.

Question 19

pathogen

Answer 19

Pathogen- A biological agent that causes disease or illness to its host.

Question 20

2. Explain the terms: parasitism, primary host, intermediate host and vector with reference to Blood Fluke and Malaria

Answer 20

Parasitism is a relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism. primary host is one in which a parasite reaches maturity and reproduces sexually. An intermediate host is one in which the parasite does not do this. a vector is an organism that does not cause disease itself, but which spreads infection by conveying pathogens from one host to another. Blood fluke is a non-infectious disease caused by a parasitic flatworms which can live inside people. They enter the human body after hatching in water contaminated by faeces, and ride on a tiny snail host that burrows through the skin. In this case, the human body is the primary host because the parasite reaches maturity and reproduces sexually. Similarly, malaria is also a non-infectious disease caused by a parasite. The parasite which causes malaria requires two different hosts—a vertebrate intermediate host, such as a human, and an insect primary host, also known as the vector. For the types of malaria which infect humans and other mammals, the vector is always a mosquito. People with Malaria or blood fluke generally suffer with many symptoms and typically very sick with high fevers, shaking chills, and flu-like illness because parasites lives off of another organism, the host, harming it and possibly causing death.

Question 21

3. Explain four ways in which parasites can avoid the body’s defences.

Answer 21

1. Antigenic variation – Some protozoan parasites shed and then vary their surface antigens upon entering a host so that the host does not produce antibodies against the parasite.
2. Antigenic mimicry – Some parasites such as blood fluke can take up host molecules and insert them into their own surface layers so that the immune system of their host can no longer recognise them as ‘non-self’.
3. Evade destruction by macrophages – they evade enzymatic breakdown which normally occurs in macrophages and hence avoid detection by the immune system.
4. Interfere with the normal immune response as seen in AIDS

Question 22

4. Briefly outline key features of the following groups of pathogens and give examples of diseases caused by: bacteria

Answer 22

Bacteria – Bacteria are prokaryotic cells and are usually heterotrophs. Many replicates very rapidly, undergoing a complete replication cycle (binary fission. Bacteria play important ecological roles such as decomposers and as organisms in the nitrogen cycle. Many bacteria are parasites of other living organisms. Some are major pathogens of humans, crops, and animals. The symptoms of bacterial disease result from the destruction of cells and tissues by bacterial enzymes, irritation by bacterial waste products, reactions to bacterial toxins that interfere with normal cellular functions, and the exaggerated immune responses of the sufferer to the foreign cells. Bacterial toxins can remain dangerous long after all bacteria have died. Pathogenic bacteria in humans include those that cause typhoid fever, tetanus, pneumonia, and tuberculosis. The diseases can be asymptomatic. These people are known as carriers. Different species of bacteria are identified by a number of physical and chemical properties such as shape, organisation, the presence or absence of a capsule, mobility, requirement for oxygen, nutritional requirements and Gram staining characteristics.

Question 23

Briefly outline key features of the following groups of pathogens and give examples of diseases caused by: protozoans

Answer 23

Protozoans - Protozoan infections are parasitic diseases caused by organisms formerly classified in the Kingdom Protozoa. Three classes of protozoans have members that are pathogenic to animals: flagellates (e.g., Trypanosoma, which causes sleeping sickness), sporozoans (e.g., Plasmodium, which causes malaria) and sarcodinians (e.g., Entamoeba histolytica, which causes amoebic dysentery)

Question 24

Briefly outline key features of the following groups of pathogens and give examples of diseases caused by: fungi

Answer 24

ungi - Fungi causes diseases such as rust and ergot in cereals, and Dutch elm disease. In humans, fungi can cause athlete’s foot (tinea), ringworm and thrush. Fungi are miulticellular heterotrophs which aquire nutrients by absorbing food outside the body by using digestive systems. Fungi is constructed of unites called Hypae which are minute thread that make up tabular walls which surround plasma and cytoplasm. The units form interwoven mates called mycelium. Parasitic fungi absorb nutrients from cells of living hosts. Direct contact is usually involved in transmission of these skin pathogens.
Plant breeders are continually developing new varieties of wheat that are resistant to rusts and smuts because diseases are continually evolving into new strains that can infect the new varieties. If baked into rye bread, ergot can cause nervous spasms, psychotic delusions, convulsions and gangrene, often leading to death. On the beneficial side, ergot in very small doses has proved useful in the treatment of migraine headaches and inducing birth as it causes the smooth muscle of blood vessels and the uterus to contract. Some fungi produce toxins that can be extremely poisonous to humans. Other fungal products, such as cyclosporine, have become immensely important tools in medicine. Discovered in the 1970s, cyclosporine was the first immunosuppressive drug. It blocks an important signal causing T cells (lymphocytes) to divide and is used mainly to prevent rejection of transplants. Many fungi produce antibiotics, such as penicillin, presumably as a defence against bacteria that are abundant in soil.

Question 25

Briefly outline key features of the following groups of pathogens and give examples of diseases caused by: worms

Answer 25

``` Worms affect both plants & animals, and make up 2 major Phylum’s, Platyhelminths and nematodes. Platyhelminths include worms like tapeworms while nematodes includes words like round worms, hookworms, pinworms etc. Single host (direct) and Multiple host (indirect) infections. ```

Question 26

Briefly outline key features of the following groups of pathogens and give examples of diseases caused by: Viruses

Answer 26

Viruses are non-cellular agents that infect all types of organisms. They are obligate intracellular parasites, meaning they cannot replicate outside of cells. They are not classified as living organisms and they are not cells. However, they can organise their own replication and can direct the construction of a surrounding protein coat. The idea that viruses might be extremely small cellular organisms was dispelled when the tobacco mosaic virus was crystallised, and its structure examined. The viruses that infect bacteria are called bacteriophages. A single virus particle (virion) is composed of genetic material, either DNA or RNA, enclosed in a protein coat known as a capsid. Viruses do not have cytoplasm, membranes or any organelles. Some viruses have additional outer layers of protein and may become wrapped in host cell membrane as they bud out of their host cell. The genetic material of viruses may be double-stranded DNA (as in cellular organisms), single-stranded DNA, double-stranded RNA (ribonucleic acid) or single-stranded RNA. Viruses produce new virions by taking over the metabolic pathways of the host cell. Viruses also have 2 types of life cycles.

Question 27

Briefly outline key features of the following groups of pathogens and give examples of diseases caused by: prions

Answer 27

Prions - Prions are now known to cause diseases such as Creutzfeldt-Jakob disease (CJD) and kuru in humans, mad cow disease, and scrapie in sheep. Prions are even more unusual than viruses. They are proteinaceous infectious particles. Like viruses they can replicate in cells, but they are composed of protein only. In cells, only nucleic acids can replicate and code for new proteins. Prions consist of a protein, called PrP for Prion Protein. There is both normal PrP and disease-causing PrP, known as scrapie PrP. The amino acid composition of the two forms is similar. The difference seems to be in the shape of the protein. Contact between scrapie PrP and normal PrP causes the normal PrP to fl ip into the disease shape. In an infected mammal the nervous system accumulates large amounts of scrapie PrP and slowly degenerates.

Question 28

5. Compare antibiotics, antiseptics and disinfectants. Give some examples of each.

Answer 28

Antiseptics and antibiotics are used to treat infection on humans which disinfectant is used to destroy microbes on objects and surfaces. Antiseptics are used to treat peoples tissue injuries while antibiotics are used to fight microbes in the body’s immune system by adding antibodies to one’s immune system thus aiding the boding in fighting off the diseases. Antiseptics use predominantly 70% alcohol and has a lower killing power than disinfectant because they are designed to destroy microbes on the skin without damaging tissue. On the other hand, disinfectants used chlorine and ammonium (bleach) which are much more effective in killing/stopping the growth of microbes. An example of an antibiotic is penicillin used to treat bacterial infections like ear infection, or doxycycline for pneumonia infections. An example of disinfectants includes bleach and mouth wash. An example of antiseptics includes Dettol, tea tree oil etc, commonly used on cuts and abrasions.  

Question 29

6. Explain what is meant by non-specific defences and give examples of external and internal non-specific defences.

Answer 29

There are 2 lines of nonspecific defences that are available for the body to use. The first of these are external defences, such as mucous, skin, and hair. The second line of defense is the internal one, including inflammatory, temperature, protein, and white blood cell responses. Nonspecific defences include physical and chemical barriers, the inflammatory response, and interferons. Physical barriers include the intact skin and mucous membranes. These barriers are aided by various antimicrobial chemicals in tissue and fluids. An example of such a substance is lysozyme, an enzyme present in tears that destroys the cell membranes of certain bacteria.

Question 30

7. Explain what is meant by the specific immune response. How is this different when recognising foreign particles compared to the non-specific defences?

Answer 30

While healthy phagocytes are critical to good health, they are unable to address certain infectious threats. Specific immunity is a complement to the function of phagocytes and other elements of the innate immune system. In contrast to innate immunity, specific immunity allows for a targeted response against a specific pathogen. Only vertebrates have specific immune responses. Two types of white blood cells called lymphocytes are produced in the bone marrow with the two most common are T cells and B cells. An antigen triggers a response from T and B cells specific to millions of different antigens. For example, if a person received a blood transfusion that did not match his blood type, it could trigger reactions from T and B cells. B cells can mature and differentiate into plasma cells that produce a protein called an antibody that can target a particular antigen. However, they rely on T cells to provide a signal that they should begin the process of maturation. When a properly informed B cell recognizes the antigen it is coded to respond to, it divides and produces many plasma cells. The plasma cells then secrete large numbers of antibodies, which fight specific antigens circulating in the blood. T cells are activated when a particular phagocyte known as an antigen-presenting cell (APC) displays the antigen to which the T cell is specific. This blended cell (mostly human but displaying an antigen to the T cell) is a trigger for the various elements of the specific immune response. A subtype of T cell known as a T helper cell performs a number of roles. T helper cells release chemicals to · Help activate B cells to divide into plasma cells · Call in phagocytes to destroy microbes · Activate killer T cells Once activated, killer T cells recognize infected body cells and destroy them. Regulatory T cells (also called suppressor T cells) help to control the immune response. They recognize when a threat has been contained and then send out signals to stop the attack.

Question 31

8. Summarise the three lines of defence.

Answer 31

The first line of defence (or outside defence system) includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These include your skin, tears, mucus, cilia, stomach acid, urine flow, ‘friendly’ bacteria and white blood cells called neutrophils. Pathogenic (disease-causing) microorganisms must make it past this first line of defence. If this defence is broken, the second line of defence within your body is activated. The skin is the largest organ of your body. It acts as a barrier between invaders (pathogens) and your body. Skin forms a waterproof mechanical barrier. Microorganisms that live all over your skin can’t get through your skin unless it’s broken. Epidermis cells are tightly packed (minimising the entry of bacteria, and cells shed, removing any attached microorganisms. Secretions from sweat glands also gice skin a pH od 3-5 (acidic) which prevents the colonisation of bacteria. Your nose, mouth and eyes are obvious entry points for pathogens. However, tears, mucus and saliva contain an enzyme that breaks down the cell wall of many bacteria. Those that are not killed immediately are trapped in mucus and swallowed. Special cells line and protect the nose, throat and other passages within your body. The inner lining of your gut and lungs also produces mucus to trap invading pathogens. Hair is another form of defence, because it resists cuts and alerts us to insects and parasites that might be infectious ie. Mosquitoes. Very fine hairs (cilia) lining your windpipe move mucus and trapped particles away from your lungs. Particles can be bacteria or material such as dust or smoke. Stomach acid kills bacteria and parasites that have been swallowed. Your urine flow flushes out pathogens from the bladder area. Antimicrobial proteins makes up another important feature in the 1st line of defence. They are found in secretions such as mucous, salvia, tears eg. Enzyme lysozymes. Lysozymes are a protein that digests bacterial call walls killing the bacteria. They prevent bacteria from entering the upper respiratory tract and openings around the eyes. Once barriers like the skin and mucosal membranes are breached, the immune system’s second line of defence against invading pathogens is its non-specific (innate) response. This response is rapid, short-lived and generic, and it lacks any memory of previous infections. Through pattern recognition receptors, cells involved in the innate response can recognise pathogens like bacteria and viruses. Important components of innate immunity include: Natural killer cells Natural inclination is to kill everything they meet. What stops them is the recognition of self markers – major histocompatibility complex (MHC) proteins – on the surface of the cells they make contact with. Virus-infected cells and cancer cells have fewer of these markers and so are more likely than healthy self cells to be killed. NK cells release chemicals called cytokines, which alert and attract other immune cells. Phagocytes Cells that engulf – or phagocytose – microbes or other cells that are infected, damaged or dying. Most cells are capable of phagocytosis, but the immune system employs specialist phagocytes like macrophages and neutrophils to deal with foreign matter. They begin by wrapping themselves around the offender, enclosing it in a vesicle called a phagosome before breaking down the contents with hydrolytic enzymes. The remains are presented (so-called antigen presentation) to other specialised immune cells that initiate a more targeted immune response. Inflammation When the receptors of cells involved in the non-specific immune system are engaged by pathogens, the cells release molecules that trigger inflammation. Increased blood flow brings in more cells to deal with the problem, and also leads to swelling and pain, which alert you to the fact that something is wrong. Greater blood flow also causes an increase in temperature, which can inhibit the replication of some bacteria and viruses. While healthy phagocytes are critical to good health, they are unable to address certain infectious threats. Specific immunity is a complement to the function of phagocytes and other elements of the innate immune system. In contrast to innate immunity, specific immunity allows for a targeted response against a specific pathogen. Only vertebrates have specific immune responses. Two types of white blood cells called lymphocytes are produced in the bone marrow with the two most common are T cells and B cells. An antigen triggers a response from T and B cells specific to millions of different antigens. For example, if a person received a blood transfusion that did not match his blood type, it could trigger reactions from T and B cells. B cells can mature and differentiate into plasma cells that produce a protein called an antibody that can target a particular antigen. However, they rely on T cells to provide a signal that they should begin the process of maturation. When a properly informed B cell recognizes the antigen it is coded to respond to, it divides and produces many plasma cells. The plasma cells then secrete large numbers of antibodies, which fight specific antigens circulating in the blood. T cells are activated when a particular phagocyte known as an antigen-presenting cell (APC) displays the antigen to which the T cell is specific. This blended cell (mostly human but displaying an antigen to the T cell) is a trigger for the various elements of the specific immune response. A subtype of T cell known as a T helper cell performs a number of roles. T helper cells release chemicals to · Help activate B cells to divide into plasma cells · Call in phagocytes to destroy microbes · Activate killer T cells Once activated, killer T cells recognize infected body cells and destroy them. Regulatory T cells (also called suppressor T cells) help to control the immune response. They recognize when a threat has been contained and then send out signals to stop the attack.

Question 32

9. Explain and give examples of: active immunity (natural and artificial) and passive immunity (natural and artificial).

Answer 32

Both active and passive immunity deal with antibodies. The main difference between active and passive immunity is that active immunity is developed by the production of antibodies by person’s own body whereas passive immunity is developed by the antibodies which are produced outside. Active immunity results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Exposure to the disease organism can occur through infection with the actual disease (resulting in natural immunity), or introduction of a killed or weakened form of the disease organism through vaccination (Artificial immunity). Either way, if an immune person encounters that disease in the future, their immune system will recognize it and immediately produce the antibodies needed to fight it. Active immunity is long-lasting, and sometimes lifelong. Passive immunity is the transfer of active humoral immunity of ready-made antibodies. it is provided when a person is given antibodies to a disease rather than producing them through his or her own immune system. A newborn baby acquires passive immunity naturally from its mother through the placenta. A person can also get passive immunity artificially through antibody-containing blood products such as immune globulin, which may be given when immediate protection from a specific disease is needed. This is the major advantage to passive immunity; protection is immediate, whereas active immunity takes time (usually several weeks) to develop. However, passive immunity lasts only for a few weeks or months. Only active immunity is long-lasting.

Question 33

10. Explain how primary lymphoid organs and secondary lymphoid organs differ. ).

Answer 33

Lymphoid organs are organs that facilitated the 3rd line of defence. In primary lymphoid organs, immature lymphocytes differentiate to mature ones into an antigen sensitive lymphocyte and after maturation, lymphocytes migrate to secondary lymphoid organs. The primary lymphoid organs include bone marrow and thymus which both provide micro-environments for the development and maturation of T-lymphocytes. The secondary organs provide the sites for the interaction of lymphocytes with the antigen, which then proliferate to become effector cells. Such organs include the spleen, lymph nodes and mucosal associated lymphoid tissue (MALT).

Question 34

11. What are antigens and antibodies?

Answer 34

Antigen is a substance that the immune system perceives as being foreign or dangerous. Antibodies, also called immunoglobulins, are proteins manufactured by the body that help fight against foreign substances called antigens. When an antigen enters the body, it stimulates the immune system to produce antibodies. (The immune system is the body's natural defense system.)

Question 35

12. Explain in detail the difference between cell-mediated immunity (T cells) and humoral immunity (B cells). Draw a flow chart that includes the activation of both T and B cells and how the different cells interact to produce a strong immune response. (UB)

Answer 35

According to the composition of the adaptive system, it can be further divided into two categories; humoral immunity and cell-mediated immunity. Humoral immunity is the primary defence system against extracellular pathogens which drives by the B lymphocytes. On the other hand, cell mediated immunity is the primary defence system against intracellular pathogens which drives by the T lymphocytes. What is Humoral Immunity? Humoral immunity, also known as antibody-mediated immunity, is one branch of adaptative immunity that mediates by antibodies secreted by the B- lymphocyte cells. Humoral immunity works against specific pathogens outside the cells (extracellular pathogens). B-cells are bone marrow-derived, and each cell makes only one kind of antibody which specifically reacts on a particular pathogen. DNA rearrangement makes sure the antibody diversity. Moreover, these antibodies can directly neutralize viruses. For certain pathogens, the antibodies bind to target the cells and signal phagocytes or other white blood cells or other defence mechanisms to attack them. Thus, B cell activation, B cell proliferation and antigen-antibody interaction are three main mechanisms of humoral immunity.  

Question 36

What is Cell Mediated Immunity?

Answer 36

Cell mediated immunity is the immunity that mediates by T-cell antigen receptors made by thymus-derived T-cells. As the name implies, T-cells themselves specifically bind with the antigens, instead of releasing the receptors from the cell body. However, there is no antibody involvement in cell mediated immunity. Furthermore, cell mediated immunity works mainly for intracellular pathogens. Cell mediated immunity is mainly facilitated by the T helper cells and cytotoxic T lymphocytes. Each T-cell makes only one kind of T-cell antigen receptor. Thus, the t-cell receptor has four proteins, namely, two large (α) and two small (β) chains. Each chain has constant and variable regions. The variable regions determine the specificity of the receptor toward a particular pathogen while the variable regions project outside helping to bind the T-cells to the antigen cell. Thus, the cell-mediated immune system is important as it eliminates tumour cells before they can grow and spread very much. This process is known as ‘immunological surveillance’. Also, when tissue from an unrelated individual is introduced into another individual, this immune system will respond and kill the transplanted tissue immediately.

Question 37

What are the Similarities Between Humoral and Cell Mediated Immunity?

Answer 37

· Humoral and Cell Mediated Immunity are two types of adaptative immunity. · Both immunity types activate upon the exposure to foreign antigens. · They effectively defence our body against a variety of pathogens. · Also, both immunities create immunological memory against antigens. · Besides, they both systems do not work properly in immune-compromised people.

Question 38

What is the Difference Between Humoral and Cell Mediated Immunity?

Answer 38

The key difference between humoral and cell mediated immunity is the production of antibodies. Humoral immunity mediates by the antibodies produced by B lymphocytes while cell mediated immunity does not involve antibodies. Furthermore, humoral immunity mainly works against extracellular pathogens identified by the antibodies while cell mediated immunity works against intracellular pathogens identified by the T cell receptors. Hence, this is also a difference between humoral and cell mediated immunity. Another important difference between humoral and cell mediated immunity is that the humoral immunity does not provide immunity against cancers while the cell mediated immunity provides immunity against cancers

Question 39

Summary – Humoral vs Cell Mediated Immunity

Answer 39

Humoral and cell mediated immunity are two types of active or adaptative immunity. The key difference between humoral and cell mediated immunity is that the humoral immunity facilitates by the antibodies produced by B lymphocytes. In contrast, cell mediated immunity does not facilitate by the antibodies. It is mediated by TH cells and cytotoxic T lymphocytes. Another difference between humoral and cell mediated immunity is that the humoral immunity works against extracellular antigens while the cell mediated immunity works against intracellular antigens.  

Question 40

13. Outline the stages of the inflammation response. Include the role of mast cells and histamine.

Answer 40

nflamation involves swelling, redness, pain, heat and loss of function. This response is triggered by tissue injury and prevents the spreading of damaging agents. It disposes of cell debris and sets the stage for tissue repair. In response to exposure to a perceived pathogen, mast cells set off a rapid inflammatory response to outside invaders, such as germs, viruses, and parasites. Mast cells have the capacity to directly kill these organisms or to stimulate the production and release of substances that will destroy the pathogen. A mast cell is a migrant cell of connective tissue that contains many granules rich in histamine and heparin. Histamine is an amine that is produced as part of a local immune response to cause inflammation. It also performs several important functions in the bowel and acts as a neurotransmitter or chemical messenger that carries signals from one nerve to another.

Question 41

14. Outline the steps involved in an allergic response.

Answer 41

There are three stages to the allergic response: In the first stage, the immune system encounters the foreign substance and identifies it as an invader. macrophages surround and break up the invading allergen. It then primes the immune system to recognize this invader as an enemy that needs to be destroyed in future encounters. This stage is known as sensitization. The subsequent stages are mast cell activation, and prolonged immune activation. STAGE 1 — SENSITIZATION The first time an allergen meets the immune system, no allergic reaction occurs. Instead, the immune system prepares itself for future encounters with the allergen. Scavenger cells called macrophages surround and break up the invading allergen. The macrophages then display the allergen fragments on their cell walls to specialized white blood cells, called T lymphocytes, which are the main orchestrators of the body's immune reaction. The T cells secrete a signaling chemical called interleukin-4, which activates other white blood cells known as B lymphocytes. These cells secrete antibodies specific for that particular allergen. These antibodies, called immunoglobulin E (IgE) receptors, are attached to cells in the immune system, called mast cells and basophils. Individuals prone to allergies are known to have abnormally high levels of IgE antibodies. STAGE 2 — MAST CELL ACTIVATION Stage 2, or mast cell activation, represents a later encounter between the allergen and the immune system wher IgE antibodies on mast cells, constructed during the sensitization phase, recognize the allergen and bind to the invader. Once the allergen is bound to the receptor, granules in the mast cells release their contents/mediators such as histamine, platelet-activating factor, prostaglandins, and leukotrienes. Mediators are what actually trigger the allergy attack. Histamine stimulates mucus production and causes redness, swelling, and inflammation. Prostaglandins constrict airways and enlarge blood vessels. STAGE 3 — LATE PHASE INFLAMMATORY RESPONSE In Stage 3 tissue mast cells and neighboring cells produce chemical messengers that signal circulating basophils, eosinophils, and other cells to migrate into that tissue, to help fight the foreign material. These recruited immune cells secrete chemicals of their own that sustain inflammation, cause tissue damage, and recruit yet more immune cells. This phase occurs several hours after exposure and can last for hours and even days.