Vaccines and Immunity Flashcards
What is the role of T lymphocytes (T cells)?
- involved in the specific immune response
(second line of defense after a pathogen enters the bloodstream)
Where are T cells made and where do they mature?
- bone marrow
- mature in the thymus.
What is the cell-mediated response?
the response involving T cells reacting specifically to antigens presented on antigen-presenting cells
What are antigen-presenting cells (APCs)?
Cells that display non-self antigens on their surface
Examples of APC’s?
- Infected cells presenting viral antigens.
- Macrophages after phagocytosis.
- Cells of transplanted organs.
- Abnormal cells like cancer cells.
Why is it called the cell-mediated response?
T cells only respond to antigens on the surface of cells, not free-floating antigens in bodily fluids
What happens when a T helper cell binds to an antigen-presenting cell?
The receptor on the T helper cell binds to the antigen on the APC, activating the T helper cell
What occurs after T helper cells are activated?
They divide by mitosis to form clones of T helper cells
What happens to the cloned T helper cells?
They can:
- Stimulate B cells (humoral response).
- Stimulate macrophages for more phagocytosis.
- Become memory T cells.
- Become cytotoxic (killer) T cells.
What do cytotoxic (killer) T cells do?
destroy infected or abnormal cells by releasing perforin a protein that creates pores in the cell membrane, causing cell death
How does perforin work?
- It embeds into the cell membrane of an infected cell, creating a pore.
- Substances enter and exit the cell, leading to its death.
Why are cytotoxic T cells important in viral infections?
They kill virus-infected cells to prevent the virus from replicating and spreading.
What causes a sore throat during a viral infection?
Cytotoxic T cells destroy infected throat cells, preventing viral replication but causing soreness
What are the key types of cells involved in the cell-mediated response?
- Helper T cells: Stimulate other immune cells.
- Memory T cells: Retain information about antigens.
- Cytotoxic T cells: Destroy infected or abnormal cells.
What are the steps in the cell-mediated response.
- Antigen from pathogen is displayed on the cell surface of body cells
- t cells with correct specific receptor bind with antigen and are activated
- Helper T cells divide by mitosis
- Helper T cells stimulate B cells, macrophages, or differentiate into memory/cytotoxic T cells.
- Cytotoxic T cells release perforin to destroy infected cells.
What is phagocytosis?
nonspecific immune response where phagocytes (e.g., macrophages) engulf and destroy pathogens or non-self substances
What are phagocytes?
- also known as macrophages
- white blood cells that carry out phagocytosis
- found in the blood and tissues
What does “nonspecific response” mean in phagocytosis?
phagocytes respond the same way to any non-self substance, regardless of the specific antigen
What is the role of white blood cells in the immune response?
provides nonspecific responses (e.g phagocytosis by phagocytes) and specific responses (e.g., lymphocytes).
What attracts phagocytes to pathogens or abnormal cells?
Chemicals, toxins, or debris released by pathogens or abnormal cells attract phagocytes
How do phagocytes bind to pathogens?
Receptors on the phagocyte’s surface bind to antigens or chemicals on the pathogen’s surface.
What happens after a phagocyte binds to a pathogen?
The phagocyte changes shape to engulf the pathogen, forming a vesicle around it called a phagosome
What is a phagosome?
the vesicle within a phagocyte that contains the engulfed pathogen
What is the role of lysosomes in phagocytosis?
fuse with the phagosome, releasing lysozymes (enzymes) into it to break down the pathogen.
What is lysozyme, and what does it do?
an enzyme in lysosomes that hydrolyzes and destroys pathogens inside the phagosome
What happens to the broken-down pathogen in the phagosome?
The soluble products are absorbed and recycled by the phagocyte.
What is an antigen-presenting cell (APC)?
After phagocytosis, the phagocyte displays the pathogen’s antigen on its surface, becoming an antigen-presenting cell (APC)
What is the significance of antigen-presenting cells (APCs)?
presents antigens to T cells, triggering a specific immune response
Summary of the process of phagocytosis
- Phagocytes detect and move towards pathogen chemicals.
- They bind to the pathogen and engulf it, forming a phagosome.
- Lysosomes fuse with the phagosome, releasing lysozymes to hydrolyze the pathogen.
- Soluble products are absorbed, and the phagocyte becomes an APC.
Why is phagocytosis considered nonspecific?
It occurs the same way regardless of the type of foreign particle, whether it’s an abnormal cell, pathogen, or transplant cell.
What is the humoral response?
a specific immune response involving B cells and antibodies
Where are B cells made and matured?
bone marrow
What do B cells do?
produce antibodies and participate in specific immune responses by responding to particular antigens
How do B cells recognize antigens?
Each B cell has specific antibodies on its surface that are complementary to a particular antigen
What happens when a B cell binds to its complementary antigen?
- The B cell takes in the antigen by endocytosis
- presents it on its surface and
- becomes activated by a helper T cell.
What is clonal selection?
the process where an activated B cell undergoes mitosis to produce identical clones which differentiate into plasma cells and memory B cells
What do plasma cells do?
produce large quantities of antibodies to help destroy pathogens
What do memory B cells do?
- remain in the body for decades
- rapidly divide into plasma cells if they encounter the same antigen again
What is the difference between the primary and secondary immune response?
- Primary Response: Slower and produces fewer antibodies when encountering a pathogen for the first time
- Secondary Response: Faster and produces more antibodies due to memory B cells
Why don’t we get symptoms during the secondary immune response?
Memory B cells enable rapid production of antibodies, destroying the pathogen before symptoms develop
What is the structure of an antibody?
- quaternary proteins
- made of four polypeptide chains (two heavy, two light)
- variable region binds to specific antigens.
- constant region remains the same in all antibodies
What is agglutination?
- the clumping together of pathogens when antibodies bind to multiple antigens
- makes it easier for phagocytes to engulf them.
How do antibodies help destroy pathogens?
- Antibodies bind to antigens, forming antigen-antibody complexes.
- Agglutination occurs, making pathogens easier for phagocytes to locate and engulf.
What are the two main types of cells produced by clonal selection?
- Plasma Cells: Produce antibodies.
- Memory B Cells: Provide long-term immunity by rapidly producing plasma cells if re-exposed to the antigen.
Process of the humoral response
B cells bind to antigens and are activated by helper T cells.
Activated B cells undergo clonal selection to produce plasma cells and memory cells.
Plasma cells release antibodies, and memory cells provide long-term immunity.
Antibodies bind to antigens, forming complexes and leading to agglutination, which aids phagocytes in destroying pathogens.
What is active immunity?
occurs when the body is exposed to a pathogen, producing memory cells and antibodies for long-term protection
What allows the immune system to distinguish between self and non-self cells?
Molecules on the cell surface membrane, called antigens, act as unique markers that lymphocytes recognize
What are antigens typically made of?
Proteins with distinct 3D shapes.
What types of non-self cells can lymphocytes recognize?
- Pathogens (e.g., bacteria, fungi, viruses).
- Cells from organ transplants.
- Abnormal body cells (e.g., cancer cells).
- toxins (e.g., cholera toxins).
How do lymphocytes ensure they don’t attack self-cells during fetal development?
- Lymphocytes complementary to self-antigens are destroyed or suppressed.
-This ensures only lymphocytes targeting non-self antigens remain active.
What happens if lymphocytes mistakenly attack self-cells?
can lead to autoimmune diseases, where the immune system harms the body’s own cells
How many types of lymphocytes does the human body have?
Approximately 10 million types, each recognizing one unique antigen
Where does lymphocyte selection continue after birth?
bone marrow
What is antigen variability?
Frequent mutations in a pathogen’s DNA can change the shape of its antigens, making previous immunity or vaccines ineffective
Why is a new flu vaccine needed each year?
influenza virus mutates frequently, changing the shape of its antigens so prior vaccines or immunity no longer work
What are the key roles of antigens?
- Act as markers to identify cells.
- Trigger immune responses by lymphocytes.
What happens to lymphocytes complementary to self-cells during development?
They are destroyed or suppressed to prevent them from attacking the body
What are the consequences of antigen variability?
- Loss of immunity from prior infections.
- Ineffectiveness of previous vaccines.
What is passive immunity?
when antibodies are introduced into the body rather than being created by the immune system.
What are examples of passive immunity?
- Antibodies passed through the placenta to a fetus.
- Antibodies in breast milk for a baby.
- Antibodies injected to neutralize toxins, such as snake venom.
What are the characteristics of passive immunity?
- Fast-acting
- No memory cells are produced
- Provides no long-term immunity
What are the two types of active immunity?
- Natural active immunity: Created after infection with a pathogen.
- Artificial active immunity: Created by vaccination.
What is a vaccine?
contains a weakened or dead form of a pathogen that stimulates the immune system to produce antibodies and memory cells
How do vaccines work?
Vaccines expose lymphocytes to antigens, triggering clonal selection, clonal expansion, and differentiation into plasma cells and memory B cells
What is the role of memory B cells in immunity?
they remain in the blood for decades, enabling rapid production of antibodies upon re-exposure to the pathogen
What is herd immunity?
When enough of the population is vaccinated, it prevents the spread of a pathogen, protecting those who cannot be vaccinated
Why is herd immunity important?
- protects vulnerable individuals
- such as infants, the elderly
What are the key differences between active and passive immunity?
- Active immunity: Body produces its own antibodies; includes memory cells for long-term protection.
-Passive immunity: Antibodies are introduced externally; no memory cells or long-term protection.
What is immunity
The ability to resist infection
