IMMUNOLOGY

Detailed explanation-1: -B lymphocytes are the cells of the immune system that make antibodies to invading pathogens like viruses. They form memory cells that remember the same pathogen for faster antibody production in future infections.

Detailed explanation-2: -Memory B cells are generated during primary responses to T-dependent vaccines. They persist in the absence of antigens but do not produce antibodies (i.e., do not protect), unless reexposure to antigen drives their differentiation into antibody-producing plasma cells.

Detailed explanation-3: -Each B cell produces a single species of antibody, each with a unique antigen-binding site. When a naïve or memory B cell is activated by antigen (with the aid of a helper T cell), it proliferates and differentiates into an antibody-secreting effector cell.