Britannica Sources used in this answer

How does passive immunity differ from active immunity?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

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.

The primary difference between active and passive immunity lies in how the body acquires its defense against pathogens.

Active immunity occurs when an individual's own immune system is stimulated to produce its own antibodies and lymphocytes in response to the presence of antigens. This process can happen naturally through exposure to a pathogen or artificially through vaccination. A key feature of active immunity is the development of immunological memory, which allows the body to respond more rapidly and effectively upon re-exposure, often providing long-lasting protection.12

Passive immunity involves the transfer of pre-formed antibodies to an individual from an immune subject. Because the recipient's own immune system is not actively involved in producing these defenses, the protection is immediate but temporary and does not result in long-term immunological memory. This can occur naturally, such as through the placenta or breast milk, or artificially via the administration of immune serum globulin to treat specific infections or toxins.31