There are two primary types of immunity in humans: active immunity and passive immunity.
These two types of immunity differ significantly in how they are acquired and the duration of protection they offer. Understanding these differences is crucial for comprehending how our bodies defend against disease.
Active Immunity
Active immunity develops when the body's immune system is stimulated to produce its own antibodies in response to an antigen, such as a virus or bacteria. This can happen in two ways:
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Natural Active Immunity: This occurs when you are exposed to a disease-causing organism (pathogen) and develop the illness. Your immune system then remembers the pathogen and provides long-lasting protection against future infections. An example is developing immunity to chickenpox after having the disease.
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Artificial Active Immunity: This happens through vaccination. A vaccine contains a weakened or inactive form of a pathogen (or a part of it, like a protein) that doesn't cause illness but still triggers an immune response. The immune system produces antibodies and "memory cells" that will recognize and fight off the real pathogen if exposed in the future. Examples include vaccines for measles, mumps, rubella (MMR), and influenza.
The key characteristic of active immunity is that it is long-lasting, sometimes even lifelong. It takes time to develop, typically a few weeks, as the body needs to create its own antibodies and memory cells.
Passive Immunity
Passive immunity, on the other hand, is acquired when a person receives antibodies produced by another person or animal. This type of immunity provides immediate but temporary protection.
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Natural Passive Immunity: This occurs when antibodies are passed from mother to child. For instance, antibodies cross the placenta during pregnancy, giving the newborn some immunity against diseases the mother is immune to. Antibodies are also passed through breast milk.
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Artificial Passive Immunity: This involves receiving antibodies from an external source, such as an injection of immunoglobulin. This provides immediate protection against a specific disease or toxin. Examples include antivenom for snake bites and immunoglobulin injections after exposure to hepatitis A or rabies.
Passive immunity is short-lived, lasting only a few weeks or months, because the body doesn't produce its own antibodies. The received antibodies are eventually broken down and eliminated.
Summary
Here's a table summarizing the key differences:
Feature | Active Immunity | Passive Immunity |
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How Acquired | Body produces its own antibodies | Receiving antibodies from another source |
Onset | Slow (weeks) | Immediate |
Duration | Long-lasting (often lifelong) | Short-lived (weeks/months) |
Examples | Infection, vaccination | Maternal antibodies, immunoglobulin injections |
In conclusion, active and passive immunity are the two main types of immunity. Active immunity involves the body creating its own antibodies and provides long-lasting protection, while passive immunity involves receiving antibodies from an external source and offers temporary protection.