What does the term 'antibody transfer' typically refer to?

The term 'antibody transfer' specifically refers to passive immunity, which involves the transfer of antibodies from one individual to another. This transfer can occur naturally, such as when maternal antibodies are passed to the fetus through the placenta or to an infant through breast milk. This type of immunity provides immediate, but temporary, protection against pathogens without requiring the recipient's immune system to actively respond by producing its own antibodies.

In contrast, natural active immunity refers to the immunity that develops after exposure to a pathogen, where the individual’s immune system actively produces antibodies in response to an infection, providing long-term protection. Humoral immunity is a broader term that includes the production of antibodies by B cells in response to antigens, but it does not inherently imply the direct transfer of antibodies. Cell-mediated immunity involves T cells and does not pertain to antibody transfer; it focuses on the immune response against infected or cancerous cells.

Thus, passive immunity is the best description of the term 'antibody transfer', as it emphasizes the acquisition of antibodies from an external source rather than through the individual's immune response.