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 Responses are as follows:
Primary vs Secondary Immune Response
|Primary Immune Response
|Secondary Immune Response
|The 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.
|Appears mainly in the lymph nodes and spleen.
|Appears mainly in the bone marrow and then, in the spleen and lymph nodes.
|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.
|The antibody level reaches its peak in 7-10 days.
|The antibody level reaches its peak in 3-5 days.
|Affinity of Antibody
|Low affinity to their antigens.
|High affinity to their antigens.
|Naive B cells and T cells
|Memory B cells
|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.
|Long (4-7 days)
|Short (1-4 days)
|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.
|Amount of Antibody
|Few antibodies are produced in the primary immune response.
|100-1000 times more antibodies are produced in the secondary immune response.
|Strength of the Response
|The primary immune response is usually weaker than the secondary immune response.
|The secondary immune response is stronger.
|Antibody level declines to the point where it may be undetectable.
|The antibody level tends to remain high for longer.