Primary immune response

Primary immune response The primary immune response occurs when a pathogen comes in contact with the immune system for the first time . During this, the immune system has to learn to The immunological resistance developed by the organisms through the production of antibodies in their body is called active immunity. Active immunity is acquired through the use of a person’s immune responses, which lead to the development of memory cells. Active immunity results from an infection or an immunization. Passive immunity does not require the body to produce antibodies to antigens. The antibodies are introduced from outside into the organism. Thus, passive immunity is acquired without the activation of a person’s immune response, and therefore there is no memory. Sl.No Active Immunity Passive Immunity Active immunity is produced actively by host’s immune system. Passive immunity is received passively and there is no active host participation. It is produced due to contact with pathogen or by its antigen. It is produced due to antibodies obtained from outside. It is durable and effective in protection. It is transient and less effective. Immunological memory is present. No memory. Booster effect on subsequent dose is possible. Subsequent dose is less effective. Immunity is effective only after a short period. Immunity develops immediately. Table . Differences between active and passive immunity Sl.No Primary Immune Response Secondary Immune Response It occurs as a result of primary contact with an antigen. It occurs as a result of second and subsequent contacts with the same antigen. Antibody level reaches peak in to days. Antibody level reaches peak in to days. Prolonged period is required to establish immunity. It establishes immunity in a short time. There is rapid decline in antibody level. Antibody level remains high for longer period. It appears mainly in the lymph nodes and spleen. It appears mainly in the bone marrow, followed by the spleen and lymph nodes. Table . Differences between primary and secondary immune responses XII Std Biology-Zoology Chapter- XII Std Biology-Zoology Chapter- Human Health and Diseases Fig. . Lymphoid organs in human body Bursa of Fabricius is a primary lymphoid organ of birds. It is attached to the dorsal side of the cloaca. B lymphocytes mature in the bursa and bring about humoral immunity. Thymus The thymus is a flat and bilobed organ located behind the sternun, above the heart. Each lobe of the thymus contains numerous lobules, separated from each other by connective tissue called septa. Each lobule recognize the antigen, produce antibody against it and eventually produce memory lymphocytes. The primary immune response is slow and short-lived.