What is a lymphokine?

A lymphokine is a type of soluble protein mediator that is produced by sensitized lymphocytes in response to an antigen. These proteins are part of the immune response and play crucial roles in the communication between immune cells. When lymphocytes, such as T cells, recognize an antigen, they secrete lymphokines to modulate the immune response, activate other immune cells, and enhance the overall effectiveness of the immune reaction.

Lymphokines can influence the growth, differentiation, and activity of various cellular components of the immune system, including macrophages, B cells, and other T cells. Their ability to facilitate cell-to-cell communication is essential for orchestrating the body's defense mechanisms against pathogens and ensuring an appropriate immune response.

In contrast, other options such as hormonal proteins released by the pancreas do not relate to immune cell communication, antibodies produced by B cells represent a different class of immune proteins specific to antigens, and proteins released by neutrophils during inflammation are responses to infection or injury rather than a specific signaling function like that of lymphokines.