Final answer:
New B cell receptors are generated through V(D)J recombination, a process that rearranges gene segments to create diverse antigen-binding sites, followed by activation through Helper T cells and transformation into antibody-secreting plasma cells.
Step-by-step explanation:
Creation of a New B Cell Receptor
To create new B cell receptors (BCRs), a process called V(D)J recombination occurs, which is a type of genetic reorganization. This process is essential in developing the unique antigen-binding sites necessary for effective immune function. During B cell differentiation in the bone marrow, a DNA recombinase randomly excises variable (V), diversity (D), and joining (J) gene segments for the heavy chains, and V and J segments for the light chains. This genetic rearrangement facilitates the creation of millions of possible unique combinations for the variable regions of the BCRs.
Once a naive B cell encounters its specific antigen, it internalizes the antigen and presents it on an MHC II molecule. A Helper T cell then recognizes this complex and activates the B cell. This leads to the B cell's transformation into a plasma cell capable of secreting antibodies or into a memory B cell. The mature plasma cells secrete antibodies structurally similar to the BCR but are tailored to the antigen through transposition, resulting in a specific antibody that inactivates the antigen.