Let's learn about adaptive immunity.
The human body has a number of ways to fight off nasty pathogens.
There are 2 types of adaptive or specific immunity.
Cell mediated and antibody mediated.
This video covers antibody mediated immunity.
B lymphocytes or B cells are involved in antibody mediated or humoral immunity.
B-cells are activated by co-stimulation which involves a connection between an antigen receptor
on the B-cell and an antigen from a pathogen.
Here, an antigen from a pathogen is displayed on a macrophage which acts as an antigen presenting
cell.
Along with the antigen antigen-receptor connection, substances called cytokines are secreted by
the macrophage which also help to activate the B-cell.
Activated B-cells secrete antibodies.
Activated B-cells are called plasma cells.
Here is an antibody.
Antibodies contain constant and variable portions.
The variable portions connect with regions on antigens called antigenic determinants.
The constant region can activate a series of plasma proteins called the complement system.
Antibodies can connect to antigens and disable them.
Antibodies can bind antigens together.
Antibodies can connect to mast cells promoting the release of substances that cause inflammation.
Antibodies bound to antigens can stimulate phagocytosis.
There are several types of antibodies or immunoglobulins.
IgG antibodies are the most abundant type.
They protect against viruses and bacteria and can cross the placenta.
IgE antibodies are secreted by plasma cells in skin, GI/Respiratory tracts and tonsils.
They trigger inflammation.
IgD antibodies bind to B-Cells and function as antigen receptors.
IgA antibodies are found in sweat, saliva, intestines.
They prevent pathogens from attaching to epithelial surfaces.
IgM antibodies can activate the complement system, act as antigen receptors on B-Cells
and cause agglutination in the ABO blood typing system.
IgM antibodies can activate the complement system.
The complement system forms membrane attack complexes that drill holes in pathogens.
Antibodies activate the complememt system by way of the classical pathway.
Upon first exposure to a pathogen, the immune system produces antibodies to fight it off.
This is known as the primary immune response.
Activated B-cells clone themselves.
Some of these clones serve as memory cells that can immediately secrete antibodies if
exposed to the same pathogen.
This is called the secondary immune response.
There are 4 types of immunity.
In naturally acquired active immunity, the body is exposed to a pathogen and responds
by making antibodies.
A vaccine is a good example of artificially acquired active immunity.
Here, antigens are given and the body makes antibodies to produce immunity.
In naturally acquired passive immunity antibodies are transferred from the placenta to the fetus.
In artificially acquired passive immunity, antibodies are given to someone who's immune
system is damaged.
I hope you have learned something about antibody-mediated immunity and see you next time.