17.3 Adaptive Immunity

Lymphocytes are characterized by their large nuclei that actively absorb Wright stain and therefore appear dark colored under a microscope.

A programmed cell death is caused by the NK cell detection.

The phagocytic cells digest the debris left behind.
Control of potential infections and preventing cancer progression can be achieved with the help of NK cells.
Mast cells, natural killer cells, and white blood cells are involved in the innate immune response.

There are inactive forms of complement that are abundant in the blood and are capable of responding immediately to infections.

The complement system is related to the innate and adaptive immune system.
Complement proteins are attracted to pathogens that are already tagged by the adaptive immune system.
This "tagging" involves the attachment of antibodies to the pathogen.
The binding site for one of the complement proteins is provided by the antibodies when they attach.
After the first few complement proteins bind, a cascade of binding in a specific sequence of proteins follows in which the pathogen becomes coated.

The presence of a pathogen in the environment is a marker for the presence of complement proteins.

Certain complement proteins can cause lysis of the cells.

The innate response takes days or even weeks to become established, whereas the adaptive response is more specific to an invading pathogen.

This part of the immune system is activated when the innate immune response is insufficient.
Without information from the innate immune system, the adaptive response could not be mobilized.
T and B cells with surface binding sites specific to the pathogen increase in numbers and attack the invading pathogen.
Their attack can either kill the pathogens or cause them to die.
On reexposure, the host memory will facilitate a rapid and powerful response, because adaptive immunity also involves a memory to give the host long-term protection from reinfection with the same type of pathogen.

The red bone marrow of many flat bones contains white blood cells called Lymphocytes, which are formed with other blood cells.

B cells and T cells are the two types of immune cells.

The B cells remain in the bone marrow to mature, while the T cells migrate to thethymus, where they mature.

Maturation of a B or T cell involves becoming immune, meaning that it can recognize a specific molecule.

B and T cells that bind too strongly to the body's own cells are eliminated in order to minimize an immune response against the body's own tissues.
Those cells that react weakly to the body's own cells, but have highly specific receptors on their cell surfaces that allow them to recognize a foreign molecule, remain.
During fetal development, this process occurs.
The specificity of this receptor is determined by the genetics of the individual and is present before a foreign molecule is introduced to the body or encountered.
Genetics and not experience initially provides a vast array of cells, each capable of binding to a different foreign molecule.
The T and B cells will migrate to the spleen and lymphatic area once they are immune.
T cells are involved in the cell-mediated immune response, which targets infections, and B cells are involved in the humoral immune response, which targets infections.

A T lymphocyte is shown in this scanning electron micrograph.

T and B cells can be differentiated by probing their surface receptors.

A molecule that stimulates the immune system is called an antigen.

Not every molecule is antigenic.

B cells are involved in a chemical response to antigens present in the body by producing specific antibodies that circulate throughout the body and bind with the antigen whenever it is encountered.

The immune response is called the humoral immune response.

B cells have a variety of antigens that are binding through their variable regions.

Every B cell has a different type of antigen receptor.

The B cells migrate from the bone marrow to other parts of the body.
The B cell is sensitized when this process is complete.
A helper T cell is a type of T cell that the sensitized B cell must encounter before it is activated.
The helper T cell must have already been activated.

Thousands of identical (clonal) cells can be made when the B cell is stimulated to divide rapidly by the T cell binding to the antigen-MHC class II complex.

These daughter cells can be either memory B cells or plasma cells.
At this point, the memory B cells are inactive until another encounter with the antigen causes them to divide into a new group of cells.
The plasma cells can produce up to 100 million molecules per hour.

The agents of humoral immunity are the antibodies.

Antibodies can be found in the blood, mucus and breast milk.
Antibodies in bodily fluids can destroy pathogens before they get to cells.

The blood stream and lymphatic system are home to these antibodies.

The binding can be used to fight infections.

Antibodies can interfere with the chemical interactions required for them to bind to other cells.
The antigenic sites in the particles may clump together and prevent their proper functioning.
The complement system was destroyed by the cell bearing the antigen.
When the complexes are present, the phagocytosis of the cells is enhanced.
The presence of antibodies on the skin and mucus prevents pathogen attack.

Antibodies prevent pathogens from entering and infecting host cells by blocking key sites on the pathogen.

The neutralizing antibodies can be used to eliminate the pathogens in urine or feces.

In a process called opsonization, antibodies mark pathogens for destruction by phagocytic cells.

complement fixation is a process in which some antibodies provide a place for complement proteins to bind.

Rapid clearing of pathogens is promoted by the combination of antibodies and complement.

The antibodies in a pregnant woman's body move into the fetus.

The Immune System and Disease is used to fight a disease.

The body doesn't need time to mount its own response since this gives immediate protection.

Antibodies may prevent the antigen from binding its target, tag a pathogen for destruction by macrophages or neutrophils, or cause the complement cascade to cascade.

B cells are able to recognize pathogens, but T cells can't.

When a pathogen is detected, theseAPCs will break it down.
Antigen fragments will be taken to the surface of theAPC, where they will serve as an indicator to other immune cells.
Dendritic cells are found in the nose, lungs, stomach, and intestines.
The positions are ideal to encounter invaders.
Once activated by a pathogen, they migrate to the spleen.
Macrophages are also an example of an example of an example of an example of an example of an example of an example of an example of an example of an example of an example of an example of an example of an example of an example of an example of an example of an example The components are broken down into fragments within the phagolysosome and then loaded onto MHC class II molecules.
T cells can't respond to an object unless it is embedded in an MHC class II molecule.
The MHC class II complexes on the surfaces of theAPCs signal an invader.

An lysosome is used to partially digest a foreign antigen, which is then embedded in an MHC class II molecule for presentation at the cell surface.

The MHC class II molecule must be interacted with by immune cells to mature into functional immune cells.

Dendritic cells are part of the body's immune system.

There are many functions for T cells.

Some respond to the innate immune system by releasing cytokines.
B cells are stimulated to start the humoral response.
Some T cells are involved in suppressing immune reactions to harmless or "self" antigens, while others are directly killing the infections.

There are two main types of T cells.

The immune cells are told about potential pathogens by the th lymphocytes.
The MHC class II complexes of APCs are presented to the Th lymphocytes.
There are two populations of cells.
Th1 cells increase the activity of macrophages and other T cells.
The naive B cells are stimulated to make antibodies.

The nature of the invading pathogen and the specific types of cytokines that are produced by cells of the innate immune system determine whether a TH1 or a TH2 immune response develops.

T cells are the key component of the adaptive immune system and are used to attack and destroy cells.

The cells that protect against viral infections are the ones that are shielded from contact with the body's immune system.
In the case of proliferation of activated B cells, the TC creates a large clone of cells with one specific set of cell-surface receptors.
The clone includes active and inactive cells.
The host cells are identified by the active TC cells.
There is a delay in the adaptive immune response compared to the innate immune response because of the time required to generate a population of clonal T and B cells.

The goal of the cells is to destroy the cells that the pathogen can replicate and escape from.

The cells support the immune system to fight cancer.
The ability to identify and destroy cells and tumors is enhanced by the stimulation of the TH1 response that stimulates macrophages.

A helper T cell is activated by binding to the MHCII receptor, which causes it to release cytokines.

The humoral or the cellmediated immune response can be activated by this.

The memory component of the adaptive immune system allows for a rapid and large response to a pathogen.

As B and T cells mature into effector cells, a subset of naive populations differentiate into B and T memory cells with the same antigen specificities.

The effectors are no longer needed as the infection is cleared.
The memory cells persist in the circulation.

A B cell presents the antigen to MHC class II after binding it to the B cell receptor.

The B cell is activated by a helper T cell.
The cells are made.

Rh-positive red blood cells have the Rh antigen.

An Rh positive female can usually carry a Rh positive fetus to term.
If she has a second Rh-positive fetus, her body may launch an immune attack that causes hemolytic disease of the newborn.

B and T memory cells will circulate for a few years or even several decades if the pathogen is not encountered again in the lifetime of the individual.

If the host is exposed to the same pathogen, circulating memory cells will differentiate into different types of cells.
The time it takes for naive B and T cells to be identified and activated is one of the reasons why the adaptive immune response is delayed.
A more rapid production of immune defenses is achieved when this step is skipped.
The amount of antibody produced by memory B cells that differentiate into plasma cells is hundreds of times greater than the amount produced during the primary response.
The individual may not realize they have been exposed to the disease, as the rapid and dramatic antibody response may stop the infection before it can even become established.

The primary response to infections is the production of antibodies.

After re-exposure to the same pathogen, memory cells differentiate into cells that produce more antibodies for a longer period of time.

Exposure to noninfectious antigens, derived from known pathogens, causes a mild primary immune response.

The immune response to vaccination can still be seen as illness by the host.
The reaction is similar to a secondary exposure when an individual is exposed to the same pathogen.
Some vaccine courses involve one or more booster vaccinations to mimic repeat exposures, because each reinfection creates more memory cells and increased resistance to the pathogen.

Lymph moves through the body through the lymphatic system, which is made up of vessels, ducts, and organs.

The regulation, maturation, and inter communication of immune factors occur at specific sites, despite the immune system being characterized by circulating cells throughout the body.

Immune cells and other factors are transported through the blood.
About 0.1 percent of the cells in the blood are leukocytes, which include monocytes.
Red blood cells are found in most cells in the body.
Extravasation is a process that allows cells of the immune system to travel between the blood and lymphatic systems.

Stem cells in the bone marrow give rise to the immune system.

B cell maturation occurs in the bone marrow, whereas progenitor cells migrate from the bone marrow and develop into naive T cells in the organ called the thymus.

T and B lymphocytes travel to different destinations.

Large populations of T and B cells, dendritic cells, and macrophages can be found in the Lymph nodes scattered throughout the body.
The lymph is returned to circulation after the antigens are removed.
The immune cells in the lysies capture, process, and inform the immune cells around them of potential pathogens.

The liquid passes through the afferent vessels and leaves through the efferent vessels, which are filled with lymphocytes that purge infecting cells.

Foreign particles trapped in the blood can communicate with the immune system in the spleen.
The immune system is made up of activated blood cells in the spleen and immune cells in the body.
The spleen is to the blood as the lymph is to the scuplture.

The function of the spleen is to immunologically filter the blood and allow for communication between cells.

The systemic immune system is different from the mucosal immune system because of the innate and adaptive immune responses.

The first tissues onto which pathogens are deposited are the mucosa associated lymphoid tissue.
The mouth, pharynx, and esophagus are part of the mucosal tissue.

MALT is an immune system that has its own components.

MALT is a collection of tissue that is part of the body.
Many of the same cell types are used by the immune systems.
Absorptive epithelial cells take up foreign particles that make their way to MALT.