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How does humoral immunity differ from cell-mediated immunity?

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Immune stimulation by activated helper T cells — immune system Stimulation of immune response by activated helper T cells. Activated by complex interaction with molecules on the surface of a macrophage or some other antigen-presenting cell, a helper T cell proliferates into two general subtypes, T_H1 and T_H2. These in turn stimulate the complex pathways of the cell-mediated immune response and the humoral immune response, respectively.

Humoral immunity and cell-mediated immunity are two distinct but complementary branches of the adaptive immune system that function to eliminate foreign antigens.

Humoral Immunity

Humoral immunity is mediated by B cells. Upon activation, these cells differentiate into plasma cells that secrete antibodies into the body's fluids (the "humors"). These antibodies circulate through the blood and lymph to identify and neutralize pathogens—such as bacteria or viruses—that remain outside of the body's cells.12

Cell-Mediated Immunity

Cell-mediated immunity relies on the direct action of T cells rather than antibodies. This system is essential for targeting infectious agents, such as viruses or intracellular parasites, that have entered and are actively growing within host cells.13

There are two primary mechanisms for this response:
* Helper T cells: Release cytokines that enhance the ability of other immune cells, such as macrophages, to destroy microbes.3
* Cytotoxic T cells: Directly identify and kill infected host cells by inducing apoptosis or using pore-forming proteins like perforins.34

While these systems are distinct, they often cooperate; for example, T cells play a critical role in regulating B cell function during an immune response.13