Primary Immune Response:
1. It occurs as a result of primary contact with an antigen.
2. Antibody level reaches peak in 7 to 10 days.
3. Prolonged period is required to establish immunity.
4. There is rapid decline in antibody level.
5. It appears mainly in the lymph nodes and spleen.
Secondary Immune Response:
1. It occurs as a result of second and subsequent contacts with the same antigen.
2. Antibody level reaches peak in 3 to 5 days.
3. It establishes immunity in a short time.
4. Antibody level remains high for longer period.
5. It appears mainly in the bone marrow, followed by the spleen and lymph nodes.