Cell immunity Flashcards
What is the definition of a pathogen?
a harmful microbe that can damage tissues in our bodies
What is the definition of a non-specific immune response and name the types of the non-specific immune responses.
our immediate response to infection and is carried out in exactly the same way regardless of the pathogen
Physical barriers and phagocytosis
What are the physical non-specific barriers, which prevent pathogens from entering our body?
- Our body cavities (e.g. eyes, nose, mouth, genitals)
- Eyes = enzymes in tears destroy micro-organisms
- The trachea
- Our stomach
- The insides of our intestines and the surface of our skin are covered in harmless bacteria which will compete with any pathogenic organisms and reduce their ability to grow.
what is the definition of a specific immune response and what are specific immune responses?
happens after the non-specific response and is an attack aimed at a particular antigen.
It is slower and provides long term immunity
It involves the activation of two types of immune cells: T lymphocytes and B lymphocytes
How do pathogens get destroyed by phagocytosis?
Chemical products of pathogens act as attractants, causing the phagocytes to move toward the pathogen.
Phagocyte attaches to the surface of the bacteria
Engulfs bacteria to form a vesicle (phagosome)
Lysosome fuses its membrane with the phagosome and breaks the cell wall.
Lysozymes destroy ingested bacteria by hydrolysis of their cell walls.
The soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte
the phagocyte releases insoluble dissolved substances out of the cell
Why are antibodies only effective against a specific pathogen?
- Antigens have a specific shape/tertiary structure
- Which the antibodies are complementary to antigen and a antigen-antibody complex forms
What is the definition of antigens?
any part of an organism or substance that is recognised as non-self by the immune system and stimulates an immune respose
Where are lymphocytes produced?
in the bone marrow by stem cells
What are T-cells?
lymphocytes matured in the thymus gland and associated with cell-mediated immunity
What does cell-mediated immunity mean?
immunity involving body cells
How do T-lymphocytes distinguish invader cells from normal cells?
- phagocytes that have engulfed and hydrolysed a pathogen present have some of the pathogen’s antigens on their own cell-surface membrane
- body cells invaded by a virus present have some of the viral antigens on their own cell-surface membrane
- transplanted cells from individuals of the same species have different antigens on their cell -surface membrane
- cancer cells are different from normal body cells and present antigens on their cell-surface membrane
What is antigen presentation?
When macrophages expose antigens from the pathogens on their surface
How do T-cells respond to infection by a pathogen?
- When phagocytes engulf pathogens, they present antigens on its cell-surface membrane
- Receptors on a specific helper T cell fit exactly onto these antigens
- this attachment activates the T-cel to divide rapidly by mitosis and form a clone of genetically identical cells
- the cloned T cells either: develop into memory cells, stimulate phagocytes to engulf pathogens by phagocytosis, stimulate B cells to divide and secrete their antibody, or activate cytotoxic T cells.
How do cytotoxic T cells kill infected cells?
produce perforin ( a chemical protein) which makes holes in the cell-surface membrane. These holes mean the cell membrane becomes freely permeable to all substances and the cell dies as a result
What is the definition of a clone?
a group if genetically identical cells or organisms formed from a single parent
How does humoral immunity work?
B cell with complementary antibodies to the antigen on the pathogen, binds to the pathogen
B cell engulfs pathogen (endocytosis) and presents the antigens on its surface
T helper cells bind to the antigens presented and stimulate the B cell to divide by mitosis = forms clones (clonal selection)
Clones differentiate into plasma cells or memory cells
How do Memory cells (B/T) work?
made during the specific immune response after a new infection by a pathogen (called a primary infection) B and T memory cells remain in the blood if person is reinfected by the same pathogen (called a secondary infection) the memory cells will recognise the pathogen and produce antibodies RAPIDLY and to a LARGE amount therefore the pathogen is killed before it can cause harm = immunity
What are antibodies and how do they protect us?
proteins with specific binding sites synthesised by B cells. They react with an antigen on the surface of the non-self material by binding to them
What is immunological memory?
when new t helper cells develop memory cells that survive for long periods of time
Draw and label an antibody?
What makes the binding site specific to the antigen?
Each binding site consists of a sequence of amino acids that form a specific 3-D shape that bonds directly to a specific antigen
What is the scientific name of an antibody? Other than globular, what type of protein is it?
immunoglobin
it is a glycoprotein
What does the constant region do?
it is the region that determines the mechanism used to destroy the pathogen
What is the purpose of the hinge region in an antibody?
it gives flexibility to the antibody molecule which allows the antigen-binding site to be placed at different angles when binding to antigens
What is agglutination?
when antibodies can cause microbes to stick together = easier for phagocytes to engulf them
What are monoclonal antibodies?
Antibodies with the same tertiary structure
Antibody produced from identical B cells
How are monoclonal antibodies used to cure cancer?
- Monoclonal; antibodies are produced that are specific to antigens on cancer cells
- These antibodies are given to a patient and attach themselves to the receptor of the cancer cells
- they attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth
how do our body cavities protect the body from infection
our body cavities (eyes, nose, ears, mouth, and genitals) are lined with a mucus membrane that contains the enzyme lysozyme which hydrolyses the cell wall of bacteria and kills them as they burst.
how does the trachea protect the body against pathogens
The trachea (windpipe) contains goblet cells that secrete mucus. Pathogens that we inhale become trapped in the mucus, which is swept toward the stomach by the action of ciliated epithelial cells.
ow does the stomach protect the body against pathogens
Our stomach contains gastric juices which are highly acidic these will denature proteins and kill any pathogens that have been ingested in our food and drinks.
