Which cells are considered humoral immune responders?

B cells are considered the primary humoral immune responders because they are responsible for the production of antibodies, which are proteins that specifically recognize and bind to antigens such as pathogens or foreign substances. The humoral immune response is a crucial part of the adaptive immune system and plays a vital role in defending the body against infections.

Upon recognizing a specific antigen, B cells can differentiate into plasma cells, which secrete large quantities of antibodies into the bloodstream and lymphatic system. These antibodies can neutralize pathogens, opsonize them for destruction by phagocytes, and activate the complement system, leading to the elimination of the invading microorganisms.

The other cell types listed do not primarily function as humoral responders. CD4 T cells are key players in coordinating the immune response and helping both B cells and other immune cells, while CD8 T cells are primarily involved in direct cytotoxic activity against infected or cancerous cells. Natural killer cells are part of the innate immune system and are primarily concerned with targeting and destroying infected or abnormal cells without the need for prior sensitization to specific antigens.