Last Updated on July 8, 2020 by Sagar Aryal
Differences between Primary and Secondary Immune Response
In a primary immune response, naive B cells are stimulated by antigen, become activated, and differentiate into antibody-secreting cells that produce antibodies specific for the eliciting antigen. A secondary immune response is elicited when the same antigen stimulates memory B cells, leading to the production of greater quantities of specific antibodies that are produced in the primary response. Some of the differences between Primary and Secondary Immune Response are as follows:
Figure: A schematic diagram showing a primary and secondary response, Source: Textbook of Microbiology and Immunology, 2/e, Parija
S.N. | Characteristics | Primary Immune Response | Secondary Immune Response |
| 1 | Definition | Primary Immune Response is the reaction of the immune system when it contacts an antigen for the first time. | Secondary Immune Response is the reaction of the immune system when it contacts an antigen for the second and subsequent times. |
| 2 | Appearance | Appears mainly in the lymph nodes and spleen. | Appears mainly in the bone marrow and then, in the spleen and lymph nodes. |
| 3 | Occurrence | This occurs in response to the primary contact of the antigen. | This occurs in response to the second and subsequent exposure to the same antigen. |
| 4 | Antibody Peak | The antibody level reaches its peak in 7-10 days. | The antibody level reaches its peak in 3-5 days. |
| 5 | Affinity of Antibody | Low affinity to their antigens. | High affinity to their antigens. |
| 6 | Responding Cells | Naive B cells and T cells | Memory B cells |
| 7 | Antibodies | Both thymus-dependent and thymus-independent antibodies are involved in the primary immune response. | Only thymus-dependent antibodies are involved in the secondary immune response. |
| 8 | Lag Phase | Long (4-7 days) | Short (1-4 days) |
| 9 | Types of Antibodies | A large amount of IgM and a small amount of IgG are produced during the primary immune response. | A large amount of IgG, a small amount of IgM, IgA, and IgE are produced during the secondary immune response. |
| 10 | Amount of Antibody | Few antibodies are produced in the primary immune response. | 100-1000 times more antibodies are produced in the secondary immune response. |
| 11 | Strength of the Response | The primary immune response is usually weaker than secondary immune response. | The secondary immune response is stronger. |
| 12 | Antibody level | Antibody level declines to the point where it may be undetectable. | The antibody level tends to remain high for longer. |
Figure: Primary and secondary humoral immune responses, Source: Cellular and Molecular Immunology, Abbas, 9th Edition.
References
- http://www.microbiologynotes.com/differences-between-primary-and-secondary-immune-response/
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