What are those Y-shaped things floating around the cell?
Humoral Immune Response
There are actually two types of immune responses: humoral and cell-mediated. The humoral immune response involves mainly B cells and takes place in blood and lymph. You can watch an animation of the humoral immune response at this link: http://www.cancerresearch.org/resources.aspx?id=586 .
B Cell Activation
B cells must be activated by an antigen before they can fight pathogens. This happens in the sequence of events shown in Figure below . First, a B cell encounters its matching antigen and engulfs it. The B cell then displays fragments of the antigen on its surface. This attracts a helper T cell . The helper T cell binds to the B cell at the antigen site and releases cytokines that “tell” or signal the B cell to develop into a plasma cell .
B lymphocytes are further discussed at http://www.youtube.com/watch?v=Z36dUduOk1Y (14:13).
Activation of a B cell must occur before it can respond to pathogens. What role do T cells play in the activation process?
Plasma Cells and Antibody Production
Plasma cells are activated B cells that secrete antibodies. Antibodies are large, Y-shaped proteins that recognize and bind to antigens. Plasma cells are like antibody factories, producing many copies of a single type of antibody. The antibodies travel throughout the body in blood and lymph. Each antibody binds to just one kind of antigen. When it does, it forms an antigen-antibody complex (see Figure below ). The complex flags the antigen-bearing cell for destruction by phagocytosis .
The video at the link below shows how this happens. http://www.youtube.com/watch?v=lrYlZJiuf18
An antibody matches only one type of antigen.
Most plasma cells live for just a few days, but some of them live much longer. They may even survive for the lifetime of the individual. Long-living plasma cells are called memory cells. They retain a “memory” of a specific pathogen long after an infection is over. They help launch a rapid response against the pathogen if it invades the body again in the future.
- Activated B cells produce antibodies to a particular antigen.
- Memory B cells remain in the body after the immune response is over and provide immunity to pathogens bearing the antigen.
Use this resource to answer the questions that follow.
- http://www.hippocampus.org/Biology Biology for AP* Search: The Humoral Response
- What is the humoral response?
- What cells are involved in the humoral response?
- Describe the antibody-B cell-Helpter T cell complex. Include an illustration.
- How do B-cells function?
- Describe the role of Helper T cells.
- Distinguish between Effector B and Memory B cells.
- Define immunoglobulin and epitope.
- Describe antibody function.
1. How do plasma cells form, and how do they help fight pathogens?
2. If a disease destroyed a person’s helper T cells, how might this affect the ability to launch an immune response?