Question

Explain unique features of acquired immunity.

Hint:

Remember the features with the acronym \textbf{S-D-M-S}: \textbf{S}pecificity (a sniper, not a bomb), \textbf{D}iversity (a huge library of targets), \textbf{M}emory (never forgets a face), and \textbf{S}elf/Non-self Recognition (knows friend from foe).

Answer 1

Acquired (or adaptive) immunity is a specific type of defense that the body develops after exposure to an antigen (a foreign substance, typically from a pathogen). Its four unique features are:

Specificity: Acquired immunity is highly specific. The immune response generated against a particular pathogen (like the measles virus) is effective only against that pathogen. Antibodies or T-cells produced in response to one antigen will not recognize or react to a different antigen.
Diversity: The immune system is capable of recognizing and responding to an almost infinite variety of different antigens. This is due to the vast repertoire of B-lymphocytes and T-lymphocytes, each with unique receptors for a specific antigen.
Memory: A hallmark of acquired immunity is its ability to "remember" past infections. After an initial encounter with an antigen, the immune system produces memory B-cells and T-cells. If the same antigen is encountered again, these memory cells mount a secondary (anamnestic) response that is much faster, stronger, and more effective than the primary response, often preventing the disease from developing. This is the principle behind vaccination.
Discrimination between Self and Non-self: The immune system has the remarkable ability to distinguish between the body's own cells and molecules ("self") and foreign substances ("non-self"). This prevents the immune system from attacking and destroying the body's own tissues, a condition known as autoimmunity.