The principle of immunization or vaccination is based on which property of the immune system?

1. Specificity

2. Memory

3. Ability to recognize self from non-self

4. Cooperation between innate and adaptive immunity

A drug that would not be helpful in the treatment of allergies is:

Small masses of lymphatic tissue found throughout the ileum region of the small intestine are called:

What constitutes about 50% of the lymphoid tissue in the human body?