Immunity develops either naturally by infection with a foreign antigen, or artificially by vaccination.

On initial exposure to the foreign antigen, the production of antibodies develops over several days. On a 2nd exposure to the same antigen, the response is quicker as memory cells respond rapidly to produce the antibodies.  

Adaptive immunity is provided by T and B cells:

• T-Cells (cell mediated immunity)
  • Activated by the antigen presenting cells
  • Differentiate into
    • T-Helper cells –  activates B-cells
    • T-Cytotoxic cells – Bind to and kill the foreign cells with the specific antigen
    • T-Suppressor cells –  Deactivate the cells once the goal has been achieved
    • T-Memory cells  - Remain in the body to react quickly on 2nd exposure to the antigen
• B-Cells (humoral immunity)
  • Initial activation by T-Helper cells
    • Produce antibodies to specific antigen
  • Continual differentiation  of B-Cells into either
    • Memory cells (long lived)
    • Plasma cells (short lived)

Passive Immunity: This can be provided by the introduction of ‘ready made’ antibodies e.g.  antibodies crossing the placenta to protect a new born body. This protection is immediate but only short-term.  It doesn’t activate the immune response to produce an immunological memory.

For further information on Adaptive immunity you can watch the below videos: