Which statement regarding the role of B cells is accurate?

B cells play a crucial role in the adaptive immune system, particularly in humoral immunity. They are responsible for producing antibodies, which are proteins that specifically target and neutralize pathogens, such as bacteria and viruses. When B cells encounter an antigen that matches their specific receptor, they become activated, proliferate, and differentiate into plasma cells that secrete antibodies. This process not only helps in eliminating pathogens but also contributes to the formation of immunological memory, allowing for a quicker and more effective response upon subsequent exposures to the same antigen.

In contrast, the other statements do not accurately reflect the role of B cells or the overall immune response. Natural killer cells are part of the innate immune response, and while their numbers can change with age, this does not relate to the function of B cells. Immunoglobulins, or antibodies, are classified into five primary classes—IgG, IgA, IgM, IgD, and IgE—rather than seven. T lymphocytes, on the other hand, are primarily involved in cell-mediated immunity and do not participate in humoral responses, which are specifically mediated by B cells and their antibody production. This clarification reinforces the significance of B cells in the context of humoral immunity.