What is the primary role of memory cells in the immune system?

Explanation: The primary role of B cells during the humoral immune response is to produce antibodies against specific antigens on pathogens. When B cells encounter an antigen that matches their specific receptor, they become activated and differentiate into plasma cells, which then secrete large amounts of antibodies into the bloodstream.

Incorrect choices:

a. Antigen presentation to B cells is carried out by antigen-presenting cells, such as macrophages and dendritic cells, not by B cells themselves.

c. Directly attacking and killing infected cells is the role of cytotoxic T cells during cell-mediated immunity, not B cells during the humoral immune response.

d. The regulation of the immune response is mainly the function of regulatory T cells (Tregs) and other immune regulatory mechanisms, not the primary role of B cells.

Explanation: The secondary immune response is faster and more potent than the primary immune response due to the presence of memory B cells and memory T cells. These memory cells "remember" the specific antigen from a previous encounter, allowing for a quicker and more effective immune response upon re-exposure to the same antigen.

Incorrect choices:
a. The secondary immune response is faster and stronger compared to the primary immune response, not delayed and weaker.
b. The secondary immune response involves the activation of memory B cells and memory T cells, not naive B cells and T cells.
d. The primary immune response is characterized by the production of IgM antibodies initially, but during the secondary immune response, the production of IgG antibodies predominates, which are more effective in neutralizing antigens.