Defense Against Diseases Flashcards
Differences Between Innate and Adaptive Immune System
Inherited
Acquired
Non-specific
Specific
No memory
Long-term memory
Rapid
Slow
Low effectiveness
High effectiveness
Coordinated by phagocytes
Coordinted by lymphocytes
Non-Specific Defense Mechanisms and Two Forms
Mechanisms that do not distinguish between one type of pathogen and another, but respond to all of them in the same way
First line of defense consists of surface barriers that prevent the entry of pathogens into the body which is coordinated by skin and mucous membranes
Second line of defense operates once the pathogen reaches the blood which is coordinated by phagocytes
Types of Lymphocytes
T Cells:
Regulator cells that activate B cells
Made in the bone marrow
Have receptor proteins on their surfaces
B Cells:
Antibody producting cells that recognize and target a speciic pathogen
Made in the bone marow and remain until maturation
Each B cell has the ability to produce a single specific type of antibody which allows the immune system to precisely target and neutralize different pathogens
Herd Immunity
Describes how a population can be protected from a contagious disease
If more indivduals become immune to a disease, the chain of transmission starts to break. With the high ammount of immune individuals, there are fewer people susceptible to the disease. Even poeple who are not vaccinated can benefit from herd immunity as the widespread immunity in the community reduces their chances of encountering the disease. This is particularly important for people who can’t be vaccinated due to medical reasons.
Evolution of Resistance to Antibiotics
Mutations in some bacteria have evolved antibioric resistance genes, and these strains can proliferate very quickly following the initial mutation and pass the resistant genes to other bacteria. THis frequency can increase in population and thus replace non-resistant over time
Some bacteria are also naturally resistant due to the lack of peptidoglycan in cell walls and having a capsule
Plasma Cells and Memory Cells
Plasma cells produce large amounts of specific antibodies which binds to specific antigen on the pathogen to destroy them, usually last a few days
Memory cells remain in the blood to provide long-term protection. They multiply rapidly to produce an instant supply of plasma cells to procide a rapid and effective response to subsequent infections
Analyzing Percentage Change in COVID-19
Change divided by original times 100
Day 1: 1000
Day 7: 800
800-100/100*100 = -20% decrease
Zoonoses
Infectous diseases that can be transmitted from animals to humans
AIDS Causes, Effects, and Method of Transmission
HIV is the main cause of aids, wher HIV binds to T cells and destroys them which decreases their number over time. THis leads to a decrease in the amount of antibodies produced as they play an important role in stimulating B cells to produce antibodies
The immune system gets weakened and the body becomes more vulnerable to pathogens, where normally harmless microorganisms can take advantage and cause infections
Vaginal and anal intercourse, sharing hypodermic needles, cuts during childbirth, and placenta from mother to child are examples of transmission
Antibiotics
Produced by microorganisms to kill or control growth of other microorganisms
They’re effective against bacteria as it can interfere with protein synthesis which blocks metabolism processes, and prevent them from being able to form a cell wall by inhibiting the formation of peptidoglycan and inhibits nucleic acid synthesis to prevent bacteria from replicating.
Not effective against viruses as they’re non living, have no cellular structure, rely on host cell, and lack a metabolism
Not effective against humans as they have different metabolic pathways and don’t have a cell wall
Blood Proteins Involved in Defense Mechanisms
Clotting factors intitate clotting process
Thrombin converts fibrinogen into fibrin
Fibrin permits blood clotting
Antibodies made by lymphocytes are responsible for specific immunity against pathogens
Enzymes in WBC’s may digest pathogens
Specific Defense Mechanisms
Mechanisms that do distinguish between different pathogens, it’s less rapid but provides long lasting immunity
Third line of defense is specific to pathogens and provides a long-term memory against them which is coordinated by lymphocytes
Types of Antigens
Non-self markers are present on foreign bodies in the blood
Self markers are present on te surface of our own cells. WHile our immune system typically tolerates self markers, they can be problematic in blood transfusion and organ transplantation because the immune system would trigger a repsonse if they are mismatched
Antibody Structure
Y-shaped structure
Y stem is the constant region because all immunoglobulins share the same amino acid sequence, aids in the destruction of pathogens
Ends of Y are variable regions with 2 binding sites where the antigens bind to form a highly specific antigen antibody complex
What is a Pathogen
An organism or virus that causes a disease
Sealing of Cut in Skin by Blood Clotting
When a blood vessel gets cut, vasoconstriction occurs to reduce blood flow to damaged area
Damaged cells release chemicals that attract platelets to form a temporary plug, and platelets release clotting factors into the plasma at a wound site
Clotting factors cause prothrombin to turn into thrombin, and thrombin catalyzes the conversion of fibrinogen, a soluble plasma protein into an insoluble fibrous protein fibrin
The fibrin molecules then attach to one another to form a big network which form clots trapping the blood
Species Specific and Cross Species Virus
Pathogen’s capacity to cause disease is limited to host species
Pathogen ability to cause disease has a range of hosts belonging to different species, known as zoonoses
Basis of Immunity
Immunity is based on the recognition of foreign molecules
All living organisms and viruses have surface molecules, and surface molecules are unique to each organism and virus.
An individual’s immune system cand detect foreign cells by recognizing certain surface molecules (antigens) not present on the surface of its own cells
Third Line of Defense and Activation of B Cells from T Cells
A phagocyte engulfs a pathogen and becomes an antigen-presenting cell (APC), displaying the antigen on its surface. A helper T cell with a matching antigen binds to the APC, gets activated, and releases cytokines. This causes the helper T cell to proliferate, creating more helper T cells specific to the antigen which creates cytokines again, making it a positive feedback loop.
Separately, a B cell binds to the same antigen, engulfs it through endycytosis, and displays it on its surface. An activated helper T cell then binds to the B cell and releases cytokines, fully activating the B cell.
The activated B cell undergoes clonal expansion, dividing repeatedly and differentiates into plasma cells, which produce antibodies, and memory cells, which provide long-term immunity.
Differences between Primary and Secondary Response
First exposure to a specific antigen
Subsequent exposure to the same antigen
One week delay
Within hours
Weak potentcy
More potent
Short life, for only a few weeks
Long lasting, for many months
Vaccines
Vaccines trigger the immune system to make antibodies against a specific pathogen. They usually contain a weakned or killed form of the pathogen
Vaccines are injected or given orally, with the antigens in the vaccine causing the production of plasma and memory cells. The primary response is slow so the number of antibodies produced is not so high. However, the vaccinated person now has immunity due to the presence of memory cells, so if it encounters a live pathogen it recognizes the pathogen through memory cells and results in a secondary response
Primary and Secondary Response
When the pathogen is first detected, the immune system starts to produce antibodies but it takes a few ays before the number of antibodies in the blood rises to a level where it can fight the infection
In secondary response, the immune system recognizes the pathogen if the body is infected again, so the immune system can act more quickly with antibody production rising sooner
Zoonoses Transmission and Examples
Direct contact: bites, scratches or contact with infected animal. Example is rabies which is caused by dog bites
Indirect contact: contact with contaminated surfaces or environments. Example is tuberculosis caused by bacteria through inhaling airborne droplets or ingestion of meat from infected cattle
Vector-borne transmission: Insects or other organisms feed on infected animals then bite humans. Example is Japanese encephalitis which is spread by mosquitos that feed on infected pigs or wading birds
Foodborne transmission: Consuming contaminated animal food products. Example is salmonella which comes from contaminated eggs and E.coli from undercooked meat
Antibodies (Immunoglobulins)
Proteins that defend the body against pathogens by binding to specific antigens on the surface of said pathogens and stimulatinf destruction
Skin as a Primary Defense
Physical Barrier: composed of thick layer of dead cells on surface that prevent pathogen entry
Chemical Barrier: contain sebaceous glands that secrete sebum, an oily substance that helps keep the skin lubricated and waterproof. Swear glands produce sweat which contain lysozyme and creates a salty and acidic environment on the skin which inhibits microbial growth
Mucous Membrane as a Primary Defense
Physics Barrier: soft and moist areas found in the trachea, nose, vagina and urethra which are lined with goblet cells that produce sticky mucus to trap pathogens which are then expelled up the trachea and out of the body
Chemical Barrier: contain lysozyme enzymes that break down the pathogens, and lined with cilia which are capable of wave-like movements that move trapped pathogens up and out
Benefits and Dangers of Vaccination
Herd Immunity
Prevent Disease
Speed up the body’s response to disease
Allergic reactions
May produced mild symptoms of the disease
Immunity might not be life-long
Antigens
An antigen is a protein/glycoprotein displayed on the outer surface of a pathogen which stimulates immune response, acting as a recognition molecule for the immune system
Each antigen has a unique structure, which leads to production of highly specific antibodies
What is Immunity
The body’s ability to resist and eliminate an infectous disease
Lymphocytes
Responsible for specific immunity, they produce antibodies to a specific pathogen, and recognize and destroy pathogens and foreign cells
Lymphocyes are found in the bloodstream or concentrated in lymph nodes
Stages of HIV Infection
Acute HIV: flu-like symptoms that occur days to weeks after contracting HIV
Chronic HIV: dormant, can last for several years
AIDS: makes a person vulnerable to oppurtunistic infections and AIDS-defining conditions
Phagocytosis
The process by which solid materials are ingested by a cell
Phagocytes recognize pathogens as non-self based on the recognition of surface proteins that make up all cells annd viruses
The pathogen gets engulfed by phagocytoses and the pathogen gets enclosed into a membrane-bound vesicle called a phagosome
Lysosomes within the phagocytes fuse with the phagosome and release lysosomes enzymes to digest and kill the pathogens
Pathogen antigens may be presented on the surface of the phagocyte to stimulate the third line of defense
