Chapter 21 - The Immune System Flashcards
Non-Specific Defense
Triggered by a large number of different agents. Constitutes the first two lines of defense.
First Line of Defense
- skin
- mucus membranes
- saliva and tears
- cilia
Second Line of Defense
Phagocytosis and Inflammation
Granulocytes
Microphages which move into the tissues. Mast cells found throughout connective tissue, usually associated with allergic responses.
Agranulocytes
Monocytes which become macrophages. Found throughout connective tissue and line vascular and lymph vessels. Function to cleanse channels and form a surveillance system, the RE system.
Inflammation
Response of the body to any irritating agent. The overall function is to remove the source of irritation, prevent the spread of infection, and repair the damage.
4 Cardinal Signs of Inflammation
- Heat - Calor
- Redness - Rubor
- Swelling - Tubor
- Pain - Dolor
Hyperemia
An increased blood flow to the point of injury. Dilation because of chemical substances. Mast cells and basophils release chemicals if the blood is near the surface, heat is felt and redness is notices.
Swelling
Due to the accumulation of tissue fluid, swelling results in compression of the nerve endings causing pain.
Pus Formation
Injured cells release toxins attracting phagocytic cells, they congregate at the injured site, they ingest microorganisms, dead and dying cells and other debris. The cells then die, it all accumulates forming pus.
Repair
An abscess on the outside of the body ruptures and drains outside, if it’s on the inside, it ruptures and is reabsorbed by the body.
Diapedesis
Neutrophils and other WBCs are attracted to the infection site. They pass through the vessel walls into the tissues.
Chemotaxis
Directional movement of cells in response to chemicals. Towards or away from the site.
Margination
Also called adhesion. Leukocytes are clinging to the capillary walls
Opsonization
Coating a microorganism to make it’s surface rougher in preparation for phagocytosis
Histamine
Released mainly by Mast cells, basophils, and platelets. It causes vasodilation and increased capillary permeability
Kinins
Polypeptides that dilate arterioles, increase vascular permeability, act as chemotactic agents, and induce pain.
Prostaglandins
Hormones related to fatty acids, which cause vasodilation, pain, and fever
Natural Killer Cells
Large granular lymphocytes, are non-specific. They kill both tumor and virus invaded cells. They make contact with the target cell, destroying it’s membrane by releasing perforins. They are the primary defenses against very early stage cancers.
Interferon
A protein produced by cells that have been invaded by a virus. It doesn’t protect the invaded cell, but is ingested by surrounding cells and produces an antiviral protein. 3 types alpha, beta, gamma. Also have anticancer activity.
Complement
A series of plasma proteins circulate in an inactive form. When they’re activated, they become part of the specific immunity and can mediate every aspect of the inflammatory process. Non-specific activation attaches to molecules found on bacteria. It’s activated by the classical, or faster pathway, or the alternative, or slower pathway.
Fever
An increase in body temperature caused by proteins called pyrogens. A protective response because many infectious organisms don’t like heat. Many bacteria require large amounts of Fe and Zn, so during a fever the liver and spleen sequester those elements.
Specific Resistance
The third line of defence. This is immunity and is specifically targeted. Composed of cells and molecules which recognize and destroy the offending agent.
Humoral Mediated Immunity
Depends primarily on proteins called antibodies. They have to attack and neutralize a foreign body. This is a chemical attack.
Cell Mediated Immunity
Cells are the effectors of this type of immunity. They directly attack the foreign substance, which is always another cell. This is a cellular attack.
Antigens
Substances which provoke an immune response. Are very large, and this is what the immune system responds to. It’s either a protein or a complex carbohydrate.
Hapten
An incomplete antigen. It’s vey small. It can attach toanother cell to become antigenic.
Antigen Receptors
Every lymphocyte has a unique molecure on it’s membrane surface that functions as the antigen receptor. Also called epitopes. The number of receptors is called the valence number, the more on the cell, the deadlier. Each receptor is three dimensional, it will only match us with a certain antigen, it’s very particular
Antigen Presenting Cell
Macrophages, B lymphocytes, and certain dendritic cells.
T-lymphocytes
Have been processed by the thymus. About 80% of circulating lymphocytes are T-cells. They look identical but each subclass can be identified by receptors found on the surface of its membrane. Two of the main receptors are CD4 or CD8.
Helper T-Cells
The primary regulatory cell of the immune system. They do not directly kill, they are responsible for recognizing the antigen displayed by the macrophage and then signal for proper immune response. This is the cell that the AIDS virus destroys.
T H1 Cells
Releases chemical substances recruiting macrophages and stimulates TC cells to proliferate.
T H2 Cells
Direct migration of eosinophils and basophils to the site of distress. They also fight parasitic infections.
Cytotoxic T Cells
Have the ability to make contact with other cells and destroy them, especially cancer and virus infected cells
T Suppressor Cells
These cells also have a regulatory role, but directed towards suppression.
B-lymphocytes
The cells that produce Igs, they are recruited by T-helper cells. They have receptors on their membrane that react with a certain membrane. When stimulated by the antigen and the T H cell, they undergo rapid mitosis forming clones called plasma cells. These are active antibody producing cells. They look identical to T-cells, but their membrane receptors are different.
Memory Cells
Both T-cells and B-cells produce memory cells. They exist for long periods of time. If an antigen makes a second appearance, the memory cells reacts immediately.
Antigen Recognition
The cells of the immune response system must be able to identify a foreign substance, each other, and all body cells. On the surface of the cells, we have MHC antigens which are genetically controlled and only identical twins will have the same MHCs.
MHC Classes
- Class I: Found in all nucleated cells in the body.
- Class II: Found only on antigen presenting cells.
Costimulation
In order for a T cell to become activated and respond to an antigen there must be a second signal or a costimulator. The costimulator is a second site on the presenting cell that must attach to the T cell, and serves as a fail safe to prevent T cells from attacking normal cells
Anergy
A prolonged state of inactivity of an immune cell combined with an antigen, but that hasn’t received proper costimulation.
Immunoglobulins
Large complex protein molecules that belong to a class of proteins, the gamma globulins. Synthesized by B-cells after stimulation by an antigen, and are specific for that antigen.
Structure of Immunoglobulins
4 polypeptide chains. 2 heavy, or long, and 2 light, or short. Have a constant region which determines the class of antibody, and a variable region which is the binding site.
IgG
The most abundant type. It circulates in the blood and can cross the placenta. Poses resistance against viruses, bacteria, and toxins.
IgM
Another circulating antibody. Serves as the antigen receptor on the surface of B-cells. It’s big, 5 subunits. The first one released into the blood during a response. Functions in agglutinations.
IgA
Found in glandular secretions on body surfaces. Found in tears, saliva, etc. Consists of two subunits.
IgD
Found attached to the surface of B-cells and function as antigen receptors.
IgE
Non-circulating. Attaches to basophils and Mast cells. Mediates allergic responses.
Function of immunoglobulins
Usually an antibody does not destroy directly, they mark the antigen for destruction.
Precipitation
Soluble molecules, mostly proteins, such as bacteria toxins precipitate out of solution and precipitate out in masses which make them easier to digest by phagocytosis.
Agglutinins
React with antigens on the surface of cells causing them to clump. This is called capping, and also creates masses which are easy to ingest.
Neutralization
React with viruses and bacterial exotoxins. They destroy their ability to infect cell. Mostly IgG and IgA.
Lysins
Antibodies cause the break up of cells. They use complement proteins to lyse the membrane and destroy the cell. Mainly IgG and IgM. The complement is the chief ammunition.
Target Cell
A host cell that contains an intracellular parasite. A transformed cell due to either mutation, virus, or cancer. A foreign tissue graft. Always killed by a T-cell, macrophage, or NK cell.
Tolerance
The immune system normally recognizes self and does not attack its own body.
Natural Immunity
The body has been exposed to organisms by natural means. Usually a low level exposure. Includes innate immunity which is genetic
Artificial Immunity
It is acquired, usually in a vaccination. Two kinds:
- active: ex, exposure to chickenpox or a vaccine against polio
- passive: antibodies supplied by another donor. Ex, antibodies crossing the placenta, or coral snake antivenom.
Organ Transplantation
Autograft- one part of the same body to another
Isograft - between identical twins
Allograft - between members of the same species
Xenograft - from animals to humans
Autoimmune Disease
The immune system begins reactions against self antigens. The cells involved are usually cytotoxic.
Immediate Hypersensitivity
Allergy mediated by immunoglobulin. Exposure to antigens causes the synthesis of IgE.
Delayed Hypersensitivity
A CMI response. It is mediated by T cells which display either CD4 or CD8 markers. Sensitized cells release cytokines that attract and activate macrophages which then clear the antigen.
