Final answer:
T lymphocytes, or T cells, are primarily responsible for cellular-level immunity by directly attacking foreign or diseased cells, differentiating them from B cells which are involved in producing antibodies for the humoral immune response.
Step-by-step explanation:
T lymphocytes (T cells) are primarily responsible for providing cellular immunity by physically attacking foreign or diseased cells within the body. In contrast, B lymphocytes (B cells) are responsible for the production of antibodies in the humoral immune response. Notably, T cells do not produce antibodies; instead, they are involved in cell-mediated immunity. Upon exposure to pathogenic antigens, naïve T cells become activated and stimulate the cell-mediated immune response, while naïve B cells once activated start producing antibodies.
There are different subsets of T cells, such as helper T cells that aid B cells in antibody production, and cytotoxic T cells that directly attack and destroy infected or abnormal cells. Moreover, memory cells, which can be either B or T cells, form after exposure to a pathogen and enable the immune system to mount faster and more effective responses upon subsequent exposures.