Function of B Lymphocytes

The goal of B Cell activation is to produce a clone of specific plasma cells that actively secrete antibodies. Also memory cells are produced as well. As previously mentioned, there are five classes of immunoglobulins which are determined by their heavy chains. Table 7 is a brief synopsis of their function.

Primary activation of B Cells in the lymph nodes can be initiated in two ways: The B Cell receptor directly attaching to its specific antigen triggering activation, or B Cells presenting antigen to T Helper Cells (CD4 T Cells). The first case is known as T independent B Cell activation and occurs only in a minority of cases. Most activation is T Cell dependent in which the receptor-antigen complex is internalized, the antigen is then "processed," and the peptide fragments of the antigen are presented to T Cells. (This process will be described in more detail in the T Cell section). The T Helper cells will then secrete cytokines that will help stimulate cell division and cloning of the initial B cell to produce antibody-secreting plasma cells and memory cells. Remember that this activation process is only necessary during a primary response, meaning the first time that antigen is encountered. In subsequent encounters, the memory cells begin the process much more quickly. This is known as the secondary response and is the goal of adaptive immunity.

The image to the right depicts thymus (T) dependent and independent activation. Some of the other receptors shown here will be discussed in the T Cell section.