Which of the following is the final stage of B cell maturation after activation by antigen?

After activation by an antigen, the final stage of B cell maturation is the plasma cell. Plasma cells are differentiated B cells that have undergone clonal expansion and are highly specialized for producing antibodies. Once a B cell encounters the specific antigen it recognizes, it becomes activated and proliferates, ultimately differentiating into plasma cells in a process driven by signals from helper T cells and other components of the immune response.

The primary role of plasma cells is antibody secretion. They produce large quantities of antibodies specific to the antigen that triggered their activation. These antibodies then enter the bloodstream and help neutralize pathogens or mark them for destruction by other immune cells.

In contrast, large granular lymphocytes, reactive lymphocytes, and immunoblasts are associated with different stages of lymphocyte activation or function, but they do not represent the terminal stage of B cell differentiation focused on antibody production. Large granular lymphocytes are typically associated with natural killer (NK) cells, reactive lymphocytes are often seen in response to infections but do not specifically indicate full B cell maturation, and immunoblasts are activated B or T cells undergoing rapid growth and division, but they do not yet represent the fully specialized plasma cell stage.