Immunity Flashcards
Examples of plasma proteins
Serum albumin
Hormones
Antibodies
fibrin
fibrinogen
thrombin
clotting factors
Phagocytes
Engulf by endocytosis/exocytosis and digest bacteria, can squeeze through gaps of the capillary wall and escape from the bloodstream. Confer non-specific immunity. The vesicle containing the pathogen is called the phagosome. The pathogen is digested by hydrolytic enzymes from the lysosomes. The remains are expelled by exocytosis.
Platelets
cell fragments-play a role in bloo clotting
Pathogen
An organism or virus that causes disease
Species-specific pathogens
Infect members of a single species eg. polio
Pathogens that cross species barriers
A disease that can be passed to humans from other animals-emerging health concern. i.e. rabies
Antigen
Any chemical substance that stimulates an immune response/antibody production. Often proteins or polysaccharides on the surface of pathogens, cancer cells eg.
Unique molecules on the cell surface of viruses
Every species has unique surface molecules. Viruses are not living organisms and are not composed of cells. But, their surface is a protein coat called the capsid which has unique molecules. The capsid of some viruses is enveloped in a membrane taken from the plasma membrane of the host cell.
Uses of unique surface molecules
-viruses recognise and bind to the host using molecules on the host’s cells surface
-organisms recognise their own cells and cell types using surface molecules
-organisms recognise foreign cells and viruses by surface molecules that are not present in that organism-trigger the production of antibodies
ABO blood group system
Based on the presence/absence of certain antigens in the membrane of RBCs. The O, A and B antigens are different versions of the same glycoproteins. The O antigen is always present
A antigen
Formed by addition of an N-acetyl-galactosamine molecules to O antigen
B antigen
Addition of a galactose molecule to O antigen
Problems with blood transfusions
Mismatches between donor and recipient can lead to an immune response in the recipient if the recipient does not possess a glycoprotein, it produces antibodies against it. The antibodies causes agglutination of RBCs followed by hemolysis
Skin
Provides a physical barrier
Sebaceous glands secrete sebum which contains lipids, lactic acid and fatty acids which lowers the pH of the skin thus preventing bacterial growth- chemical barrier
Mucous membranes
-thin, soft areas of skin found in the nose, trachea
- secrete mucus
-mucus has anti-bacterial enzyme lysozyme
-mucus traps pathogens and particles, which are then swallowed or expelled
Blood clotting
- When the skin is cut, blood vessels are injured and bleed.
- The blood in the wound turns to a semi-solid gel which prevents both further loss of blood and entry of pathogens. This is clotting and is promoted by platelets.
- Clotting starts when platelets aggregate at the site to form a plug and clotting factors are released. Clotting involves a cascade of reactions: the product of each reaction is the catalyst for the next.
- In the last step of the cascade, the enzyme thrombin is produced and this converts the soluble protein fibrinogen to the insoluble fibrin.
- Fibrin forms a mesh which traps blood cells and forms a scab. Clots can also happen in coronary arteries when the fatty plaque deposits can cause a heart attack
Immune response
Production of antibodies by B lymphocytes. Each B lymphocyte produces one type of antibody. Antibodies are proteins that recognise specific antigens and bind to them- specific immunity
Order of antibody production
- Activation of helper T cells
- Activation of B cells
- Production of plasma cells
- Production of memory cells
Activation of helper T cells
Macrophages engulf the pathogen, digest it and display antigens from it in their plasma membrane. Antigens on the macrophage membrane are attached to MHC molecules. Helper T-cells each have an antibody-like receptor protein in their plasma membrane which binds to one specific antigen displayed by the macrophage. When the antigen binds, the helper T lymphocyte is activated
Activation of B cells
Inactive B lymphocytes have antibodies on their plasma membrane. If the antibodies match an antigen, the antigen binds to the antibody. An activated helper T lymphocyte with receptors for the same antigen can then bind to the B lymphocyte. The activated helper T lymphocyte sends a signal to the B lymphocyte, activating it
Production of plasma cells
(clonal selection)
The activated B lymphocytes divide by mitosis to form a clone of identical plasma cells-clonal selection. Plasma cells are mature activated B lymphocytes that produce large quantities of the same specific antibody and secrete it in the plasma. Plasma cells have an extensive network of rER to synthesise large amounts of an antibody to be secreted by exocytosis.
Production of memory cells
Most of the clone of B lymphocyte become active plasma cells, but a small number become memory cells. Some T cells also become memory cells. These memory cells remain inactive, but they are long-lived and persist after the activated cells and antibodies produced to fight the disease have disappeared. Memory cells repsond quickly: they become active and reproduce quickly to form a clone of plasma cells producing the specific antibody-long-term immunity
Structure of antibodies(immunoglobins)
Have a hypervariable region and a constant region. The tips of the hypervariable region bind the antigen. The constant region is the part of the molecule that aids the destruction of the pathogen
Different mechanisms used by the constant region to destroy a pathogen
-Making pathogens more recognisable to phagocytes so they are more readily engulfed
-binding to the surface of a pathogen and activating the complement system. Activation of the complement cascade leads to formation of pores in the membrane and lysis of the pathogen cell.
-Sticking pathogens together so they cannot enter host cells
-neutralising toxins produced by pathogens
-preventing viruses from docking to host cells
Vaccination
Vaccines contain weakened or killed forms of the pathogen or the antigen. They are injected. The antigens in the vaccine cause the primary immune response resulting in low antibody production and production of memory cells. When exposed to the actual pathogen the memory cells trigger a more potent secondary immune response which causes faster and greater antibody production.
Smallpox
Smallpox was the first disease for which a vaccine was tested on humans. Jenner infected an 8-year-old boy with cowpox using pus from a blister of an infected milkmaid. The boy recovered. He then infected the boy with smallpox and found that he was immune. The antibodies produced against cowpox also gave immunity to smallpox.
Reasons why Jenner’s experiment is considered as ethically unacceptable
involved deliberate infection with an extremely virulent strain
below age of consent
no lab work nor animal studies
no tests for potential side-effects
Monoclonal antibodies
Purified antibodies that are produced by a single clone of hybridoma cells, so are identical. Highly specific to one antigen
Production of monoclonal antibodies
Antigens corresponding to a desired antibody are injected into a mouse. Plasma B cells producing the desired antibody are extracted from the animal’s spleen. Tumour cells called myeloma cells are obtained from a culture. These cells grow and divide endlessly. The antibody-producing plasma cells are fused with the tumour cells to produce hybridoma cells. Hybridoma cells are cultured in a fermenter. They divide endlessly to form a clone which secretes huge amounts of one specific type of monoclonal antibody. The antibodies are extracted and purified
Uses of monoclonal antibodies
Test kits for pregnancy, malaria, HIV, antibodies for injection into rabies victim
Pregnancy test use of monoclonal antibodies
Pregnancy tests employ monoclonal antibodies to hCG.The urine of pregnant women uniquely contains hCG a protein secreted by the developing embryo and later by the placenta
Active immunity
The individual is exposed to the antigen, antibodies are produced by the organism itself and memory cells are formed.
Through encountering the pathogen itself or by vaccination
Passive immunity
An organism receives antibodies from an external source
Through breast milk or by injection of antibodies
Allergen
A substance in the environment that triggers an immune response although it is normally harmless.
Allergy
Reaction by the immune system to such substances- a severe systemic allergic reaction is called anaphylaxis and can be fatal.
Histamine
Causes the symptoms associated with an allergic reaction. It causes small blood vessels in the infected area to dilate and increase permeability.
Types of WBCs that secrete histamine
-Basophils: a type of WBC that circulate in the blood
-Mast cells: similar to basophils but are found in connective tissue.
Symptoms associated with allergies
Tissue inflammation, itching, mucus secretion, sneezing
Human Immunodeficiency virus
Has RNA as genetic material. Infects helper T lymphocytes. Results in gradual destruction of lymphocytes and progressive decrease in antibody production. Over time antibody production becomes very ineffective and this can lead to AIDS. AIDS causes a person to be susceptible to many other infectious diseases which would be fought off by a healthy immune system
AIDS
An accumulation of opportunistic diseases
HIV transmission
Blood transfusion, sexual intercourse, sharing hypodermic needles, from mother to baby
Antibiotics
Chemicals that inhibit the growth of bacteria. They block processes which only occur in prokaryotes eg. cell wall formation, bacterial DNA replication. Produced by saprotrophic fungi. Some strains of bacteria have acquired resistance to one or more antibiotics.
Reasons why antibiotics cannot treat viral infections
Viruses are non-living. They lack a metabolism and rely on the metabolic pathways of the host to carry out their processes and to reproduce.
Measures to minimise antibiotic resistance
No antibiotic prescription for non-serious cases, high standards of hygiene at hospitals, no usage of antibiotics by farmers
Testing penicillin
Penicillin was discovered in the fungus Penicillium by Alexander Fleming. Florey and Chain developed a method to produce penicillin from the fungus in the lab and performed experiments. They infected eight mice with bacteria that causes pneumonia. Four were given the antibiotic while the others did not. The four untreated died and the rest survived. They tested it on a human patient and after 4 days of treatment he improved.
