Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Immunity is the body's ability to resist infection by the production of specific antibodies or through the action of specialized white blood cells like -lymphocytes and -lymphocytes.
Active Immunity: This occurs when the body's own immune system produces antibodies in response to an antigen. It can be natural (exposure to a pathogen) or artificial (vaccination). This process results in the creation of memory cells ( and ), providing long-term protection.
Passive Immunity: This is a short-term defense acquired by the transfer of antibodies from another individual. Examples include natural passive immunity (antibodies passing through the placenta or in breast milk) and artificial passive immunity (injection of antitoxins). No memory cells are produced.
Vaccination: A method of inducing artificial active immunity by introducing weakened, dead, or fragmented pathogens () into the body to stimulate a primary immune response without causing disease.
The Primary vs. Secondary Response: The secondary immune response is characterized by a shorter lag phase, a faster rate of antibody production, and a higher peak concentration of antibodies () compared to the primary response.
Antigens () are proteins or glycoproteins on the surface of pathogens that trigger an immune response, while Antibodies () are -shaped proteins (immunoglobulins) produced by plasma cells that bind to specific antigens.
📐Formulae
💡Examples
Problem 1:
A patient is bitten by a venomous snake and is immediately injected with an antivenom. Is this an example of active or passive immunity? Explain why the patient will not be immune to the same snake venom if bitten again a year later.
Solution:
This is an example of artificial passive immunity.
Explanation:
The antivenom contains pre-formed antibodies () that neutralize the toxin () immediately. Because the patient's own immune system did not produce these antibodies, no memory cells () were created. Therefore, the protection is temporary as the injected antibodies eventually break down, leaving no long-term immunity for future exposures.
Problem 2:
Compare the antibody concentration over time between a child who naturally catches Measles and a child who receives the vaccine.
Solution:
Both children develop active immunity.
Explanation:
In both cases, the body identifies the Measles antigens () and stimulates lymphocytes to produce antibodies. The vaccine uses a weakened form of the virus to trigger the primary response safely. Both children will develop memory cells, meaning that upon a second exposure to the 'wild' virus, their antibody concentration will rise rapidly via a secondary response, preventing the disease.