Final answer:
Passive immunity is acquired through the transfer of antibodies to an individual without requiring their own immune response. This can happen naturally during fetal development or through breastfeeding, and it can also be acquired artificially through injections. However, passive immunity does not provide long-lasting protection due to the lack of immunological memory.
Step-by-step explanation:
Passive immunity occurs when antibodies are transferred to an individual without them having to mount their own immune response. This can happen naturally during fetal development, when IgG antibodies are transferred from the mother to the fetus via the placenta, providing protection against infections. It can also happen through breastfeeding, where IgA antibodies are passed from the mother to the newborn through breast milk.
In addition, passive immunity can be acquired artificially through injections of immunoglobulins taken from animals previously exposed to a specific pathogen.
However, one downside of passive immunity is the lack of development of immunological memory. Once the transferred antibodies degrade, the individual is no longer protected against that specific pathogen.