Primary Vs. Secondary Immune Response

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Differences between Primary and Secondary Immune Response

The primary immune response occurs when an antigen comes in contact to the immune system for the first time. During this time the immune system has to learn to recognize antigen and how to make antibody against it and eventually produce memory lymphocytes.

The secondary immune response occurs when the second time (3rd, 4th, etc.) the person is exposed to the same antigen. At this point immunological memory has been established and the immune system can start making antibodies immediately.

Primary Vs. Secondary Immune Response

S.N. Primary immune response Secondary immune response
1. This occurs as a result of primary contact with an antigen. This occurs as a result of second and subsequent exposure of the same antigen
2 Responding cell is naïve B-cell and T-cell. Responding cell is memory cell.
3 Lag phase is often longer (4-7 days), sometimes as long as weeks or months. Lag phase is shorter (1-4 days) due to the presence of memory cell.
4 Level of antibody reaches peak in 7 to 10 days. Level of antibody reaches peak in 3 to 5 days.
5 It takes longer time to establish immunity. Takes shorter time to establish immunity.
6 First antibody produced is mainly IgM. Although small amount of IgG are also produced. Mainly IgG antibody is produced. Although sometimes small amount of IgM are produced. Other immunoglobulins such as IgA and in the case of allergy IgE are produced.
7 Amount of antibody produced depends on nature of antigen. Usually produced in low amount. Usually 100-1000 times more antibodies are produced.
8 Antibody level declines rapidly. Antibody level remain high for longer period.
9. Affinity of antibody is lower for its antigen. Antibodies have greater affinity for antigen.
10 Primary response appears mainly in the lymph nodes and spleen. Secondary response appears mainly in the bone marrow, followed by the spleen and lymph nodes.
11 Both Thymus dependent and Thymus independent antigen gives primary immune response. Only Thymus-dependent antigen gives secondary immune response.

Differences between Primary and Secondary Immune Response

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