T and B cells are classified as which of the following?

T and B cells are classified as lymphocytes, which are a type of white blood cell that plays a crucial role in the immune system. Lymphocytes are integral to the body's defense mechanisms, particularly in recognizing and responding to pathogens such as viruses and bacteria.

T cells, which mature in the thymus, are primarily involved in cell-mediated immunity. They can kill infected host cells, activate other immune cells, and regulate immune responses. B cells, on the other hand, are primarily responsible for humoral immunity and produce antibodies that bind to antigens, marking them for destruction.

The other options do not accurately describe T and B cells. Antigens are substances that can provoke an immune response, while fungus-infected cells would refer to host cells that have been compromised by a fungal infection, rather than a specific classification of immune cells. Therefore, the identification of T and B cells as lymphocytes encapsulates their primary role and function within the immune system.