Specific Defense
This is coordinated activites of T cells and B cells, which respond to the presence of specifc antigens.
T Cells
These are responsible for cell-medicated immunity (cellular immunity), which defends against abnormal cells and pathogens inside cells.
B Cells
These provide antibody-mediated immunity (humoral immunity), which defends against antigens and pathogens in body fluids.
Four Properties of specific Immunity
Specificity, Memory, Versatility, and Tolerance.
Specificity
This is a specific defense is activated by a specific anitgen, and the immune response targets that particular antigen and no others. This results from the activation of appropriate lymphocytes and the production of antibodies with targeted effects. It oc
Memory
During an initial response to an antigen, lymphocytes that are sensitive to its presence undergo repeated cycles of cell divisions.
First Memory Cell Group
One group of cells attacks the invader immediately.
Second Memory Cell Group
Another group remains inactive unless it is exposed to the same antigen at a later date. These inactive memory cells enable your immune system to "remember" antigens it has previously encountered, and to launch a faster, stronger, and longer-lasting count
Versatility
The immune system must be ready to confront any antigen at any time. This results in part from the large diversity of lymphocytes present in the body, and in part from the variability in the structure of synthesized antibodies.
Tolerance
The immune system is said to exhibit this toward normal body antigens. The immune response targets foreign cells and compounds, but it generally ignores normal tissues.
T Cells
These are involved in cell mediated immunity.
Cytotoxic T Cells
These cells enter peripheral tissues and directly attack antigens physically and chemically.
Helper T Cells
These cells stimulate the responses of both T cells and B cells. Helper T cells are vital to the immune response; because B cells must be activated by these cells before B cells can produce antibodies. The reduction in these cell populations that occurs i
Suppressor T Cells
These cells inhibit T cell and B cell activities and moderate the immune response.
Before an immune response can begin...
T cells must first be activated by exposure to an antigen.
Antigen Presentation
This occurs when an antigen-glycoprotein combination capable of activating T cells appears in the plasma membrane. The structure of these glycoproteins is genetically determined.
Major Histocompatibility Complex (MHC)
The genes controlling glycoprotein synthesis are located along one portion of chromosome number 6, in a region known as the major histocompatibility complex (MHC). Thus, these membrane glycoproteins are called MHC proteins, or human leukocytes antigens (H
Class I MHC
When a foreign antigen is presented via an MHC of this class, it instructs the immune system to kill the cell carrying the antigen.
Class II MHC
A foreign antigen presented via an MHC class II instructs the immune system to get rid of the antigen.
Class I Antigen Presentation
These proteins are continuously synthesized and exported to the plasma membrane in vesicles created at the Golgi apparatus.
As they form, Class I proteins pick up small peptides from the surrounding cytoplasm and carry them to the cell surface. If the cel
Class II antigen Presentation
These proteins are present only in the membranes of antigen-presenting cells and lymphocytes. Antigen presenting cells (APCs) are specialized cells responsible for activating T cell defenses against foreign cells (including bacteria) and foreign proteins.
Antigen Presenting Cells
1.) Free and Fixed macrophages in connective tissues.
2.) The Kupffer cells of the liver.
3.) The microglia in the CNS.
4.) The dendritic (Langerhans) cells of the skin (non phagocytic).
5.)The dendritic cells of the lymph nodes and spleen (non phagocytic
Antigen Processing
Phagocytic APCs engulf and break down pathogens. This creates antigenic fragments, which are then bound to Class II MHC proteins and inserted into the plasma membrane. Class II MHC appear in the plasma membrane only the cell is processing antigens. Exposu
Antigen Recognition
If an MHC protein contains any antigen other than the specific target of a particular kind of T cell, the T cell remains inactive. However, if the MHC protein contains the antigen that the T cell is programmed to detect, binding will occur. THIS SIMPLY PR
Cluster of Differentiation (CD Markers)
These are membrane proteins involved in a large class. Whether a T cell responds to antigens held by Class I or Class II proteins depends on the structure of the T cell plasma membrane.
CD8 Markers
These markers are found on cytotoxic T cells and suppressor T cells, which together make this cell. They respond to antigens presented by Class I MHC proteins.
CD4 Markers
These are found on helper T cells, these cells respond to antigens presented by Class II MHC proteins.
Costimulation
This serves to confirm the initial activation site. A T cell must bind to a stimulating cell at a second site before activation can occur.
Costimulation Proteins
These appear in the presenting cell only if that cell has engulfed antigens or is infected by viruses. Many costimulation proteins are structurally related to cytokines released by activated lymphocytes. Costimulation proteins typically stimulate transcri
Activation of CD8 Cells
Two different classes of CD8 T cells are activated by exposure to antigens bound to Class I MHC proteins. One type of CD8 T cell responds quickly, giving rise to large numbers of cytotoxic T cells and cytotoxic memory T cells. The other type of CD8 T cell
Cytotoxic T Cells
AKA Killer Cells. These seek out and destroy abnormal and infected cells. These cells are highly mobile and roam throughout injured tissues.
When a cytotoxic T cell encounters its target antigens bound to class I MHC proteins of another cell, it immediate
Cytotoxic T Cell Target Destruction: First
Destroy the antigenic plasma membrane through the release of perforins
Cytotoxic T Cell Target Destruction: Second
Kill the target cell by secreting a poisonous lymphotoxin.
Cytotoxic T Cell Target Destruction: Third
Activate genes in the target cells nucleus that program the cell to die. (Apoptosis)
Memory T Cells
These are produced by the same cell divisions that produce cytotoxic T cells. Thousands of these cells are produced, but they do not differentiate further the first time the antigen triggers an immune response. However, if the same antigen appears a secon
Suppressor T Cells
These suppress the responses of other T cells and B cells by secreting suppression factors. Suppression does not occur immediately, because suppressor T cell activation takes much longer than the activation of other types of cells.
In addition, upon activ
Activation of CD4 T Cells
Upon activation, CD4 T cells undergo a series of divisions that produce active helper T cells and memory T helper cells. The memory T cells remain in reserve, whereas the active T cells secrete a variety of cytokines that coordinate specific and nonspecif
Released Cytokines (from Activated Helper T Cells) do: First
Stimulate the T cell divisions that produce memory helper T cells and accelerate the maturation of cytotoxic T cells.
Released Cytokines (from Activated Helper T Cells) do: Second
Enhance nonspecific defenses by attracting macrophages to the affected area, preventing their departure, and stimulating their phagocytic activity and effectiveness.
Released Cytokines (from Activated Helper T Cells) do: Third
Attract and stimulate the activity of NK cells, providing another mechanism for the destruction of abnormal cells and pathogens.
Released Cytokines (from Activated Helper T Cells) do: Forth
Promote the activation of B cells, leading to B cell division, plasma cell maturation, and antibody production.
Sensitization
The body has million B cell populations. Each kind of B cell carries its own particular antibody molecules in its plasma membrane. If corresponding antigens appear in the interstitial fluid, they will interact with these superficial antibodies. When bindi
The Activated B Cell
These typically divides several times, producing daughter cells that differentiate into plasma cells and memory cells.
Memory B Cells
These perform the same role in antibody-mediated immunity that memory T cells perform in cell-mediated immunity. Memory B cells do not respond to a threat on first exposure. Instead, they remain in reserve to deal with future injuries or infections that i
Plasma Cells
These cells begin synthesizing and secreting large quantities of antibodies into the interstitial fluid. When stimulated by cytokines from helper T cells, a plasma cell can secrete up to million antibody molecules each hour.
Five Types of Constant Segments
1.) IgG, 2.)IgE, 3.)IgD, 4.) IgM, 5.) IgA
Specificity Of Antibody Segments
This depends on the structure of the variable segments of the light and heavy chains.
Antigen Binding Sites
The free tips of the two variable segments of an antibody molecule.
Antigen-Antibody Complex
This is formed when an antibody molecule binds to its corresponding antigen molecule.
Antigen Determinant Sites
Antibodies do not bind to the entire antigen, but to specific portions of its exposed surface regions. The specificity of the binding depends on the three-dimensional "fit" between the variable segments of the antibody molecule and the corresponding antig
Complete Antigen
This is an antigen with at least two antigenic determinant sites. Exposure to a complete antigen can lead to B cell sensitization and a subsequent immune response.
Formation of An Antigen-Antibody Complex
This formation may cause the elimination of the antigen in seven ways, they are: 1.)Neutralization, 2.)Precipitation and Agglutination, 3.)Activation of complement, 4.)Attraction of Phagocytes, 5.)Opsonization, 6.)Stimulation of Inflammation, and 7.) Prev
Neutralization
Both viruses and bacterial toxins have specific sites that must bind to target regions on body cells before they can enter or injure those cells. Antibodies may bind to those sites, making the virus or toxin incapable of attaching itself to a cell.
Immune Complex
If antigens are close together, an antibody can bind to antigenic determinants on two different antigens. In this way, antibodies can form extensive "bridges" that tie large numbers of antigens together.
Precipitation
The formation of insoluble immune complexes. When the antigen is a soluble molecule, such as a toxin, this process may create complexes that are too large to remain in solution.
Agglutination
This is the formation of large complexes, when the target antigen is on a surface of cell or virus.
Attraction Of Phagocytes
Antigens covered with antibodies attract Eosinophils, neutrophils, and macrophages. These cells phagocytize pathogens and destroy foreign or abnormal plasma membranes.
Opsonization
A coating of antibodies and complement proteins increases the effectiveness of phagocytosis. Phagocytes can bind more easily to antibodies and complement proteins on the surface of a pathogen than they can to the bare surface.
Stimulation of Inflammation
Antibodies may promote inflammation through the stimulation of basophils and mast cells.
Prevention of Bacterial and Viral Adhesion
Antibodies dissolved in saliva, mucus, and perspiration coat epithelia, providing an additional layer of defense. A covering of antibodies makes it difficult for pathogens to attach to and penetrate body surface.