Created by: Orth Sisombath, Sara Kellogg, Jill Taffe
EXAMINING HUMORAL IMMUNITY
Created by: Orth Sisombath, Sara Kellogg, Jill Taffe
EXAMINING HUMORAL IMMUNITY
The humoral immune response protects against free-floating foreign molecules (antigens). The defense involves antibodies which are secreted by B cells. The B cells are activated when a specific antigen binds to the antibody, which is located on the surface of the B cells. This activation results in the production of memory B cells and plasma B cells that are specific for that antigen. Plasma B cells release antibodies specific for the antigen. Memory B cells express the antibody on their surfaces and become important for the secondary immune response. The humoral immune response is also vital for vaccines.
Where does the humoral response begin?
The humoral response begins in the lymph nodes and the spleen. The spleen filters antigens in the blood and the lymph nodes filter antigens in the tissue. The humoral response is split into two repsonses, a primary and secondary response.
How do vaccinations work?
The main components of a vaccine can be either an inactivated bacteria causing disease or a live but weakened microorganism. When the immune system comes into contact with these components, the body generates antibodies that fight off these diseases and develop memory for future encounters with the real disease. Vaccines stimulate naive B cells to produce memory B cells that are present for a long period after the antigen has been fought off.
What are the differences between primary and secondary response in humoral immunity?
A primary humoral response results from the activation of naive lymphocytes (B cells). A primary response to antigen is characterized by a lag time, which is the period of antigen encounter until the production of plasma cells and memory cells. A secondary humoral response results in the activation of memory lymphocytes. The following table depicts the comparison of primary and secondary response:
Responding B cells to
antigen Naive B cells Memory B cells Lag period following
encounter to antigen Generally 4-7
days Generally 1-3
days Time of peak
response 7-10 days 3-5 days Magnitude of peak antibody
response Varies depending on
antigen Generally 100-1000 times
greater than primary response Antibody
affinity Low High
What is complement?
A combination of proteins called complement are important in humoral immune responses. Complement proteins are activated by the antibodies IgM and IgG, which are located on the membrane of B cells. When these antibodies recognize and bind to antigens, a conformational change of the IgM or IgG occurs. This means that its structure is slightly altered. This alteration results in the binding site for the first complement protein, Cl, to be exposed. Once Cl binds to the Ag-Ab complex, more complements proteins can also bind. Once complement proteins 1-6 bind to the Ag-Ab complex, this forms what is called the MAC complex. MAC stands for membrane attacking complex. This complex, as it implies, perforates, or punches holes in the target cell that is expressing the antigen. This allows surrounding water to flow into the cell and electrolytes to flow out of the cell resulting in cells death and therefore antigen death.