may be caused by materials in the environment (ex. cancer)
may be caused by pathogens (bacteria, viruses, fungi)
(3) viruses use a host cell to make copies of the viral DNA
diseases are spread through coughing, sneezing, physical contact, contaminated water/food, or infected animals
2. a plasmid or viral chromosome into whose genome a fragment of foreign DNA is inserted; used to introduce foreign DNA into a host cell in the cloning of DNA. (e.g. Mosquitoes)
In gene therapy, a virus itself may serve as a vector, if it has been re-engineered and is used to deliver a gene to its target cell. A “vector” in this sense is a vehicle for delivering genetic material such as DNA to a cell.
In genetics more generally, DNA by itself may be regarded as a vector, for example in particular when it is used for cell transformation. A vector in this sense is a DNA construct, such as a plasmid or a bacterial artificial chromosome, that contains an origin of replication.
Another mechanism is the fact that the outter layer of our skin, the epidermis, is very dry. And you know, in order for life to sustain itself you need water. Our skin is dry on purpose, to prevent the growth of bacteria – who love warm, moist envirnoments! (i.e. like the inside of us!)
Beneficial bacteria that live on the skin provides protection by releasing acids and wastes to kill off unwanted microorganisms. (Chemical)
The layer of overlapping dead cells on the surface of the skin prevents pathogens from entering the body. A break in the skin gives pathogens access to body tissues. If this happens blood clots then form a temporary barrier until new skin seals the wound.
An antigen refers to the protein on the surface of a cell (bacterium, fungus or virus) that our bodies recognize as a foreign substance and triggers the immune system into producing antibodies specific to that antigen. This means that if in the future the same antigen is again introduced, our immune system will recognize, remember and produce the right antibodies to “deal” with the intruders.
(2) Second line of defense- Leucocytes (white blood cells)
(3) Third line of defense – specific immune response
(2) Mucous membranes – line the entrances to the body such as in the respiratory tract entrances. Mucus produced by these membranes traps foreign particles and directs them out of the body.
(3) Hairs and cilia – (nasal hairs) trap dust and dirt; (microscopic cilia) line some mucous membranes and direct foreign particles out of the body.
(4) Gastric juice, vaginal secretions and urine – acidic fluids that have a protective function.
(5) Tears, sweat and saliva – body fluids which possess some anti-bacterial properties.
(6) Cerumen (ear wax) – produced in the ear canal and protects the canal by trapping dirt and dust particles.
The specific immune response is a mechanism that is activated by the presence of pathogens and foreign substances. These are known as antigens. Even transplanted tissue from another person, or parts of pathogens like the flagella of a bacterium, are recognised as antigens.
The body’s immune system can determine which antigens are part of its own body structure. These antigens are known as self-antigens opens in a new window. These do not stimulate an immune response.
Non-self antigens opens in a new window are the foreign substances that do stimulate an immune response.
The presence of a non-self antigen can trigger the production of specific proteins called antibodies opens in a new window. These are special proteins that are secreted by specific lymphocytes and have a specific molecular shape that matches the molecular shape of an antigen. The shape of the antibody gives it the ability to combine with and inactivate the antigen. When an antibody combines with an antigen the result is an antigen-antibody complex.
This means that:
More blood is coming to the site of the infection, bringing with it more white blood cells of the immune system
2. Then, the white blood cells are let out of the blood capillaries and into the affected tissue.
This extra blood makes the area red (as more blood means that the area looks red) and swollen (more blood and liquid leaving the blood and entering the tissue fluid surrounding the body cells).
The area will also become hot (as the extra blood is also carrying heat with it) and painful (because the tissues will be swollen with the blood).
Inflammation also attracts white blood cells to the area.
T-cells = Thymus
(2) Memory B cells are formed from activated B cells that are specific to the antigen encountered during the primary immune response. These cells are able to live for a long time, and can respond quickly following a second exposure to the same antigen.
(3) There are also two other B cells, B-1 cells and B-2 cells. read more @ http://wenliang.myweb.uga.edu/mystudy/immunology/ScienceOfImmunology/TypesofBcells.html
(2) Helper T cells
(3) Memory T cells
a secondary immune response refers to a re-encounter of the same virus/bacteria against which you have memory T cells and B cells. since the memory cells have seen the bug before, they can respond very rapdily and robustly, preventing you from feeling sick.
2. Destroy abnormal (cancerous)
3. Protect from pathogens & foreign molecules: parasites, bacteria, viruses
2. Nonspecific Resistance (Innate Immunity)
3. Specific Resistance (Acquired Immunity)
The antibodies are transported through the blood and the lymph to the pathogen invasion site.
The body contains millions of different B cells, each able to respond to one specific antigen.
(2) Gastric juice in the stomach destroys bacteria and most toxins because the gastric juice is highly acidic (pH 2-3)
(3) Saliva dilutes the number of microorganisms and washes the teeth and mouth
(4) Acidity on skin inhibit bacterial growth
(5) Sebum (unsaturated fatty acids) provides a protective film on the skin and inhibits growth
(6) Hyaluronic acid is a gelatinous substance that slows the spread of noxious agents
(1) Phagocytic cells ingest and destroy all microbes that pass into body tissues.
(2) Inflammation brings more white blood cells to the site where the microbes have invaded. The inflammatory response produces swelling, redness, heat, pain
(3) Fever inhibits bacterial growth and increases the rate of tissue repair during an infection
Most antigens are proteins that serve as the stimulus to produce an immune response. The term “antigen” comes from ANTI-body GENerating substances.
Here are the steps in an immune response:
When an antigen is detected by a macrophage (as describe above under phagocytosis), this causes the T-cells to become activated.
The activation of T-cells by a specific antigen is called cell-mediated immunity. The body contains millions of different T-cells, each able to respond to one specific antigen.
The T-cells secrete interleukin 2. Interleukin 2 causes the proliferation of certain cytotoxic T cells and B cells.
From here, the immune response follows 2 paths: one path uses cytotoxic T cells and the other uses B cells.
2. Activating complement – Complement is a group of plasma proteins made by the liver that normally are inactive in the body. An antigen-antibody complex triggers a series of reactions that activates these proteins. Some of the activated proteins can cluster together to form a pore or channel that inserts into a microbe’s plasma membrane.This lyses (ruptures) the cell. Other complement proteins can cause chemotaxis and inflammation, both of which increase the number of white blood cells at the site of invasion.
3. Precipitating antigens – Sometimes the antibodies can bind to the same free antigen to cross-link them. This causes the antigen to precipitate out of solution, making it easier for phagocytic cells to ingest them by phagocytosis (as describe above).
Also, the antigens within the cells walls of the bacteria can cross-link, causes the bacteria to clump together in a process called agglutination, again making it easier for phagocytic cells to ingest them by phagocytosis.
4. Facilitating phagocytosis – The antigen-antibody complex signals phagocytic cells to attack. The complex also binds to the surface of macrophages to further facilitate phagocytosis.