Which of the following immune disorders is characterized by the presence of chronic, widespread pain, fatigue, and tender points in specific areas of the body?

Explanation: B cells are specialized in producing antibodies against specific antigens. When B cells encounter a pathogen or foreign substance with a matching antigen, they become activated and differentiate into plasma cells. Plasma cells then secrete large amounts of antibodies, which can recognize and neutralize the pathogen.

Incorrect choices:

a. B cells do not directly attack and kill infected cells. That role is primarily performed by cytotoxic T cells during cell-mediated immunity.

c. Regulatory T cells (Tregs) are responsible for regulating the immune response to prevent excessive inflammation and maintain immune homeostasis.

d. B cells recognize antigens presented by antigen-presenting cells like macrophages, but their primary function is to produce antibodies, not to recognize antigens directly.

Explanation: Memory in the immune system refers to the ability of immune cells, particularly memory B cells and memory T cells, to recognize and respond more quickly and effectively to specific antigens upon subsequent exposure. This leads to a faster and stronger secondary immune response.

Incorrect choices:
b. The ability of immune cells to differentiate between self and non-self antigens refers to the concept of immune tolerance, which helps prevent the immune system from attacking the body's own cells and tissues.
c. The process of phagocytosis by macrophages is a mechanism by which immune cells engulf and destroy pathogens and cellular debris, but it is not directly related to memory in the immune system.
d. The ability of B cells to produce antibodies is an essential part of the primary immune response, but it is not specific to memory in the immune system.