Primary and Secondary Immune Responses: What’s the Difference?
During an initial immune response, antigen activates naive B cells, which then develop into antibody-secreting cells which make antibodies unique for the antigen that triggered the response. While the same antigen stimulates memory B cells, a secondary immunological response is induced, resulting in the generation of more specific antibodies than in the first response.
Differences Between Primary and Secondary Immune Response
|Characteristics||Primary Immune Response||Secondary Immune Response|
|Definition||The primary immune response is the reaction of the immune system when it comes into contact with an antigen for the first time.||The immune system’s reaction when it comes into contact with an antigen for the second and subsequent time is known as secondary immunological response.|
It is most commonly detected in lymph nodes and the spleen.
The bone marrow is the most affected, followed by the spleen and lymph nodes.
|Occurrence||This occurs as a result of the antigen’s initial contact.|
This occurs after a second and subsequent encounter with the same antigen.
The antibody level reaches its peak in 7-10 days.
The antibody level reaches its peak in 3-5 days.
|Affinity of Antibody|
They have a poor affinity for the antigens they are exposed to.
|They have a strong preference for their antigens.|
|Responding Cells||B and T cells are naive||Memory B cells|
|Antibodies||The major immune response involves both thymus-dependent and thymus-independent antibodies.|
In the secondary immune response, only thymus-dependent antibodies are involved.
|Lag Phase||For a long time (4-7 days)|
In summary (1-4 days)
|Types of Antibodies||During the main immunological response, a considerable amount of IgM and a modest amount of IgG are produced.||During the secondary immune response, a considerable amount of IgG and a little amount of IgM, IgA, and IgE are created.|
|Amount of Antibody||In the first immune response, only a few antibodies are generated.||The subsequent immune response produces 100-1000 times extra antibodies.|
|Strength of the Response||A significant amount of IgM and a minor amount of IgG are produced during the major immunological response.|
A significant amount of IgG and a minor amount of IgM, IgA, and IgE are produced during the secondary immune response.
|Antibody level||The antibody level drops to the point where it may be undetectable.||Antibody levels tend to remain elevated for a longer period of time.|
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