viruses, cancer and immunology Flashcards
Small amounts of genetic material surrounded by a protein envelope
Viruses
[yung genetic material can either be RNA or DNA. cannot be both]
- can be deadly (Ebola and human immunodeficiency virus (HIV))
- can be merely annoying - nonfatal (Rhinovirus, causes common colds)
why are viruses called pathogen
because they can infect and cause harm to living things, such as
- bacteria
- plants
- animals
viruses are small particles made of 2 main parts
- nucleic acid (DNA or RNA)
- protein
This is the complete virus particle, the whole virus.
Virion
This is the genetic material at the center of the virus, which contains the instructions for making new viruses.
Nucleic acid
This is the protein coat that surrounds and protects the nucleic acid.
Capsid
This is the combination of the nucleic acid and the capsid together.
Nucleocapsid
Layer that surrounds the nucleocapsid and is present in HIV
Membrane envelope
- This layer helps the virus enter a host cell.
Help viruses attach themselves to the host cell
Protein spikes
it is the process where a virus infects a cell, makes copies of itself, and then destroys the cell to release those copies.
lytic pathway
briefly explain the lytic pathway
Virus binds to the cell membrane and releases its DNA into the cell
DNA is:
* Replicated by host DNA polymerases [REPLICATION]
* Transcribed by host RNA polymerases [TRANSCRIPTION]
= New virions produced and released from the cell
how does a virus attach to the host cell before it can penetrate
binding of 1of the spike proteins on the envelope of the virus to a specific receptor on the host cell
[The virus has special “spikes” on its surface that act like keys.
These spikes find and stick to specific “locks” (receptors) on the surface of the host cell.
Once the virus attaches, it can enter the cell and start its infection process.
For example, HIV uses its spike proteins to attach to helper T cells, which are important cells in your immune system.]
it a type of virus that work in reverse compared to how normal cells make proteins.
retroviruses
- Normally, cells go from DNA → RNA → protein, but retroviruses go backward: they make DNA from RNA.
- Retroviruses have a single strand of RNA as their genetic material.
What type of genetic material do retroviruses have?
Single-stranded RNA
what happens when the virus infects the cell of the RNA
Once it infects the cell, the RNA is used as a template to make a double-stranded DNA
Enzyme: reverse transcriptase
- DNA produced by reverse transcription must be incorporated into the host DNA
- Facilitated by long terminal repeats (LTRs)
[When they infect a cell, they use an enzyme called reverse transcriptase to turn their RNA into double-stranded DNA.
This new DNA gets inserted into the host cell’s DNA with the help of special sequences called long terminal repeats (LTRs).
Once part of the host’s DNA, the virus can use the cell to make more copies of itself.]
Which retrovirus is the cause of AIDS?
causative agent: HIV (Human Immunodeficiency Virus).
What is one medical application of retroviruses in treating genetic diseases?
Retroviruses are used in gene therapy to introduce a healthy copy of a defective gene.
Method for treating a genetic disease by introducing a good copy of a defective gene
Gene therapy
retroviruses have 3 main types of genes that are important for how they work, what are they
- Coat proteins (CP):
Make up the capsid that surrounds the genetic material of a virus
(capsid, which is the protective shell around the virus’s genetic material. Think of it like the virus’s armor.) - Reverse transcriptase (RT):
Enzyme that directs the synthesis of DNA on an RNA template
( turn its RNA into DNA so it can take over the host cell.) - Envelope proteins (EP):
Found in the outer membrane of a virus and help attach to and enter host cells
*These genes are essential for the virus to survive, infect, and reproduce.
General term for many cellular and enzymatic processes that allow organisms to defend themselves from bacteria, viruses, and parasites
the immune system
- Has the ability to distinguish self from nonself
(It can tell the difference between what belongs to your body (self) and what doesn’t (nonself).
When it finds something harmful, like germs or cancer cells, it attacks and destroys them.) - Operations can be a matter of life and death
- Suppression can save lives as well as take them
(Sometimes it can become overactive and attack healthy cells, which is dangerous.
In some cases, doctors use drugs to suppress the immune system, like during organ transplants, so the body doesn’t reject the new organ.)
Causes the immune system to attack the body’s own tissues
autoimmune diseases
it can evoke violent reactions that may be life-threatening
food allergies
What is the immune system’s reaction in allergies?
it overreacts to harmless substances like pollen, dust, or certain foods.
Weakened or killed form of an infectious agent that is injected into an organism so that it will make antibodies against the true infectious agent
Vaccine
what depends on the action of vaccines
depends on exposure to the infectious agent in a weakened form
- Immune system mounts an attack and retains memory of the exposure
- In subsequent encounters, the immune system can launch a quick and effective defense
[The vaccine introduces the germ in a safe, weakened form.
The body’s immune system reacts by creating antibodies to fight the germ.
The immune system remembers how to fight that germ in the future.
If the body encounters the real, harmful version of the germ later, it can respond quickly and fight it off.]
Why does the immune system remember the germ after a vaccine?
The immune system keeps a memory of the weakened germ to recognize and fight it faster in the future.
what are the important aspects to the immunity process
Cellular level: Involves cells like white blood cells (leukocytes) that help fight off infections.
Molecular level: Involves molecules like antibodies that help recognize and destroy harmful invaders.
What are the two types of immunity?
Acquired immunity
Always-present immunity
Where do leukocytes come from?
Leukocytes arise from stem cells in the bone marrow.
what are the functions of leukocytes
Leukocytes: White blood cells
- functioning the immune system
- have the ability to leave the blood vessels and circulate in the lymphatic system
first line of defense in the immune system
innate immunity
what are the 2 main parts of the innate immunity
- Physical barriers:
* skin and mucous membranes (like in your nose), which block germs from entering the body.
They don’t need special cells to fight off germs—they just stop them from getting in. - Cells of the immune system
* special cells that help protect the body by attacking and removing harmful things.
- Dendritic cells: These are the first cells to find and recognize viruses or bacteria.
- Macrophages: These cells “eat” and break down dead cells and germs.
- Natural killer (NK) cells: These cells kill infected or cancerous cells.
where can the dendritic cells be found
skin
mucous membrane
lungs
spleen
how does the dendritic cells work
Grab and eat invaders:
They use special “suction-cup-like” receptors to grab harmful germs (like viruses or bacteria) and engulf them through a process called endocytosis (like swallowing).
Travel and alert:
After eating the germs, they travel through the lymphatic system to the spleen. There, they show pieces of the germs, called antigens, to helper T cells (TH cells).
Activate the immune system:
The helper T cells then release signals called cytokines, which help killer T cells and B cells get ready to fight off the germs.
what type of groups does dendritic cells are part of
antigen-presenting cells (APCs)
- show pieces of the germs (antigens) on their surface, which helps trigger the acquired immune system to fight the infection more effectively.
What is the role of helper T cells in the immune response?
They release cytokines that help activate killer T cells and B cells to fight off invaders.
It is the process by which cells engulf and take in substances, like germs, to destroy them.
endocytosis
what type of group does the natural killer cells belong to
belong to a group of white blood cells called lymphocytes
which come from a type of stem cell called lymphoid stem cells
what are the functions of natural killer cells
- Kills infected or cancerous cells
- Secretes cytokines that call up other cells
- Works with dendritic cells
- Helps decide whether to activate the acquired- immunity system
How do natural killer (NK) cells work with dendritic cells?
They collaborate with dendritic cells to detect and respond to threats in the body.
Acquired immunity depends on two types of lymphocytes, what are they
T cells:
* Killer T cells destroy infected cells
* Helper T cells are involved in the process of B-cell maturation
B cells:
* Play a role in the production of antibodies
how does killer T cells destroy antigen-infected cells
- Binding to them
- Releasing a protein that perforates the plasma
membranes of infected cells
Prevent the spread of viral infections by killing virus-infected host cells
killer T cells
- Some memory cells remain when infection subsides and provide immunity against later attacks from the same virus
helper T cells referred to as
CD4 cells
- Help the cell dock to the MHC of the antigen- presenting cell
- Help stimulate killer T cells and antigen-presenting cells via release of interleukins
refers to how the immune system “remembers” a past infection to respond faster if it happens again.
T-cell memory
[When the body first encounters a harmful germ (antigen), many T cells are made to fight it.
After the infection is cleared, most of these T cells die off.
A small number of memory T cells survive. These memory cells remember the germ and can reproduce faster than regular T cells, even if the germ isn’t present.
This helps the immune system respond more quickly and effectively if the body encounters the same germ again.]
Y-shaped glycoproteins
antibodies
- Consist of two identical heavy chains and two identical light chains
held together by disulfide bonds - Each heavy chain and light chain has a constant (C domain) and a
variable region (V domain)
where do V domain binds to
antigen
binding sites for antibodies on an antigen
epitopes
* Each antibody can bind to two antigens
* Each antigen has multiple binding sites for antibodies
produces from the progeny of a single cell and are specific for a singe antigen
monoclonal antibodies
- enable the production of antibodies to almost any antigen in quantity
- used to assay for biological substances that can act as antigens
- two in one antibodies: useful tools against diseases that do not respond well
to single treatments
what happens if a cell’s receptors recognize self-antigens or MHC but with low affinity
the the cell:
* Undergoes positive selection
* Differentiates into a killer T cell or a helper T cell
what happens if a cell’s receptors encounter self-antigens that are recognized with high affinity
it undergoes a process called negative selection
Process where a DP cell reacts to its own antigens and is programmed for apoptosis, or cell death
negative selection (of DP cells)
true or false:
Vertebrates have an immune system
true
[Vertebrates (animals with backbones) have an immune system to protect against infections.]
One of the leading causes of death in human beings
cancer
- Characterized by cells that grow and divide out of control, often spreading to other tissues and causing them to become cancerous
what are some key characteristics that make cancer cells different from normal cells
Uncontrolled growth:
Cancer cells keep growing and dividing even when normal cells would stop.
Ignore stop signals:
When nearby cells send signals to stop growing, cancer cells don’t listen and continue to grow.
Avoid self-destruction:
Normally, if a cell’s DNA is damaged, it would self-destruct. But cancer cells manage to avoid this process and keep surviving.
Get extra nutrients:
Cancer cells can hijack the body’s blood vessels and cause new ones to grow, which supply the cancer cells with the nutrients they need to keep growing.
Stay immortal:
Cancer cells don’t die like normal cells and can continue to live and divide for a long time.
Cancer cells can break loose from the original tumor, travel through the blood or lymph system to other parts of the body, and form new tumors. This makes cancer more dangerous and harder to treat.
Metastasis
- spread of cancer to other parts of the body
Cause changes to specific proteins that are responsible for controlling the cell cycle
DNA mutations
what are the 2 type of genes that dna mutations affect
- Tumor suppressor:
Gene that makes a protein that restricts the cell’s ability to divide - Oncogene:
Gene whose protein product stimulates growth and cell division and whose mutation causes it to be permanently active
Inhibit transcription of genes that would cause increased replication
Tumor Suppressors
- Replication and division become uncontrolled and result in tumors when a mutation occurs in any suppressor
what are the traditional approaches to treat cancer
- Surgeries to remove tumors
- Radiation and chemotherapy
- Treatment with monoclonal antibodies to target specific tumors
Form of cancer treatment that uses viruses
Virotherapy
- Virus of choice is an adenovirus, a simple DNA virus
Strategies:
* Use the virus to attack and kill the cancer cells directly
* Have the virus ferry in a gene to the cancer cell that makes the cell more susceptible to a chemotherapy agent
why is HIV deadly
because it targets helper T cells
- HIV is slow acting: Infected individuals can go years before they become aware that they have the disease
why is HIV difficult to kill
as it is difficult to find
* Rapid mutation of HIV occurs due to the inaccurate replication of HIV reverse transcriptase
* HIV changes the conformation of the gp120 protein when it binds to the CD4 receptor on a T cell
how does HIV hides from the immune system
by cloaking its outer membrane in sugars that are very similar to the natural sugars found on most of its host’s cells
[Because it can hide from the immune system. It does this by covering its outer membrane with sugars that look very similar to the natural sugars on the host’s own cells. Because of this, the immune system doesn’t easily recognize the virus as a threat and has a harder time attacking it.]
Curing HIV
- Antiviral therapy: These are drugs that stop HIV from replicating and spreading in the body.
- HAART (Highly Active Antiretroviral Therapy): This is a treatment that uses a combination of different antiviral drugs to fight HIV and stop it from multiplying.
- The Berlin Patient: One person, known as the Berlin Patient, was cured of AIDS. His cure was possible because he received a bone marrow transplant (for leukemia treatment) from a donor who had a rare genetic mutation that made them resistant to HIV.
- Ex-vivo gene therapy: This is a type of treatment where genes are modified outside the body (in a lab) and then put back into the patient to help fight the virus.
How was the Berlin Patient cured of AIDS?
He was cured through a bone marrow transplant and the donor had a genetic resistance to HIV.
