True or False: Vaccines can cause autism in children.

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: Memory cells are a type of immune cell that are formed during the body's initial encounter with a pathogen. They "remember" the specific antigen of the pathogen and allow the immune system to respond more rapidly and effectively if the same pathogen is encountered again in the future. Memory cells are responsible for providing long-term immunity.

Incorrect choices:

a. Engulfing pathogens and foreign invaders is the role of phagocytes, such as macrophages and neutrophils.

b. Initiating the inflammatory response is carried out by various immune cells, including mast cells and basophils, as part of the innate immune response.

c. Producing antibodies in response to infection is the primary role of B cells in the immune system.