Antibody class switching is a crucial process in the immune response, allowing plasma cells to change the type of antibody they produce. Initially, when B cells differentiate into plasma cells, they primarily secrete the antibody class known as IgM. This is the first antibody produced in response to an antigen. However, as activated B cells proliferate, some undergo antibody class switching, which enables them to produce different classes of antibodies, such as IgG.
Antibody class switching is defined as a genetic rearrangement process that alters the DNA of an activated B cell, specifically affecting the constant region of the antibody. This rearrangement allows the plasma cells to switch from producing IgM to IgG while maintaining specificity for the same antigen. The variable region of the antibody, which determines its specificity, remains unchanged throughout this process. Thus, both IgM and IgG antibodies can bind to the same epitope of an antigen.
During class switching, specific gene segments coding for the constant region of the antibody are deleted. For instance, when a B cell switches from IgM to IgG, the gene segments for IgM and IgD are removed, leaving the segments for IgG, IgE, and IgA intact. The gene segment that is first in line, or furthest to the left in the genetic sequence, is the one that will be expressed. In this case, if IgG is the first segment remaining, the plasma cell will produce and secrete IgG antibodies.
This process is essential for the adaptive immune response, as it allows for a more effective and targeted attack against pathogens. Understanding antibody class switching is fundamental for grasping how the immune system adapts and responds to various infections over time.
