Clonal Selection: Videos & Practice Problems

Clonal selection is a fundamental concept in immunology that explains how specific B and T cells are activated in response to an antigen. Each B and T cell has unique receptors (BCRs or TCRs) that bind to specific antigens. When an antigen enters the body, only the B and T cells that recognize this antigen are selected to proliferate. These selected cells then create clones of themselves, which can effectively combat the pathogen. This process ensures a targeted immune response, enhancing the body's ability to fight specific infections.

Clonal selection contributes to adaptive immunity by ensuring that only the B and T cells specific to an invading antigen are activated and proliferate. This selective process creates a large number of identical cells (clones) that can effectively target and eliminate the pathogen. Additionally, some of these activated B cells differentiate into memory B cells, which provide a faster and more robust response if the same antigen is encountered again in the future. This targeted and efficient response is a hallmark of adaptive immunity.

Memory B cells play a crucial role in clonal selection by providing long-term immunity. After the initial infection, some of the activated B cells differentiate into memory B cells instead of plasma cells. These memory B cells persist in the body and can quickly respond to subsequent exposures to the same antigen. Upon re-exposure, they rapidly proliferate and differentiate into plasma cells, producing antibodies more quickly and effectively than during the first encounter. This results in a faster and more efficient immune response.

BCRs (B cell receptors) and TCRs (T cell receptors) are both crucial for clonal selection, but they have different roles. BCRs are found on the surface of B cells and are responsible for recognizing and binding to specific antigens directly. Upon binding, B cells are activated, proliferate, and differentiate into plasma cells and memory B cells. TCRs, on the other hand, are found on T cells and recognize antigens that are presented by other cells via major histocompatibility complex (MHC) molecules. This recognition leads to the activation, proliferation, and differentiation of T cells, which then help in various immune responses.

Clonal selection ensures a targeted immune response by selectively activating only those B and T cells that have receptors specific to the invading antigen. When an antigen enters the body, it binds to the receptors on a small subset of B and T cells. These specific cells are then activated to proliferate and create clones of themselves. This results in a large population of cells that are all capable of recognizing and attacking the same antigen, thereby providing a highly targeted and efficient immune response against the specific pathogen.