Immunity
Resistance to disease
Pathogen
A bacterium, virus, or other microorganism that can cause disease.
Cell-mediated immune response
The branch of acquired immunity that involves the activation of cytotoxic T cells, which defend against infected cells.
Phagocytosis
A type of endocytosis in which a cell engulfs large particles or whole cells
Lymphocytes
The two types of white blood cells that are part of the body’s immune system: B lymphocytes form in the bone marrow and release antibodies that fight bacterial infections; T lymphocytes form in the thymus and other lymphatic tissue and attack cancer cells, viruses, and foreign substances.
Humoral immunity
Specific immunity produced by B cells that produce antibodies that circulate in body fluids
T lymphocytes (T cells)
Lymphocyte that matures in the thymus and acts directly against antigens in cell-mediated immune responses.
B lymphocytes (B cells)
Lymphocytes which mature in the bone marrow and that are involved in the production of antibodies
Antigens
Foreign substances that trigger the attack of antibodies in the immune response.
Non-specific immunity
Defenses that stop the invasion of pathogens; requires no previous encounter with a pathogen
Non-self
A molecule that is not recognised by the immune system as being part of the organism itself
Tertiary structure
Irregular contortions of a protein molecule due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.
Macrophages
Found within the lymph nodes, they are phagocytes that destroy bacteria, cancer cells, and other foreign matter in the lymphatic stream.
Vaccination
injection of a weakened or mild form of a pathogen to produce immunity
Bone marrow
A soft tissue inside the bone that produces blood cells
Secondary response
Production of antibodies after a second or subsequent exposure to an antigen; faster response
Plasma cells
Cells that develop from B cells and produce antibodies.
Agglutination
Clumping of microorganisms or blood cells, typically due to an antigen-antibody interaction.
Specific
The response other immune system when antigens have penetrated the bodies’ natural barriers
What is the structure of HIV?
- Core - contains genetic material (RNA) and some proteins (including enzyme reverse transcriptase)
- Capsid
- Envelope - made from the membrane stolen from the previous host cell
- Attachment proteins - allow the HIV to attach to the host helper T-cell
How does HIV replicate in helper T cells?
- Attachment proteins attach to a receptor molecule (CD4) on the membrane of helper T-cell
- Capsid is released into the cell, where it uncoats and releases the genetic material into cells cytoplasm
- Reverse transcriptase is then used to make a complementary strand of DNA from the viral RNA template
- From this, double-stranded DNA is made and inserted into human DNA
- Host cell enzymes are used to make viral proteins from viral DNA found within the human DNA
- Viral proteins are assembled into new viruses
- They bud from the cell and go on to infect other cells
How does HIV cause the symptoms of AIDS?
- HIV reduces number of T-helper cells in blood
- T-cells cannot stimulate B-cells to produce antibodies or the T-cells that kill infected cells.
=> body is unable to produce an adequate immune response and becomes susceptible to other infections and cancers.
- secondary diseases ultimately kill the patient; infections of many organs, weight loss and diarrhoea develop.
Why are antibiotics ineffective against viruses?
- They kill bacteria by interfering with their metabolic reactions (targeting bacterial enzymes and ribosomes)
- Antibiotics are only designed to target bacterial enzymes and ribosomes
- Viruses don’t have their own enzymes and ribosomes (use human)
- therefore antibiotics can’t inhibit them
What are the uses of monoclonal antibodies?
- Targeted drugs to a specific cell type - e.g cancer, monoclonal antibodies that will bind to tumour markers or cancer cells, only accumulate in areas with these present
- Medical diagnosis - e.g pregnancy testing using coloured beads etc.
