What are the primary lymphoid organs in the human body?

Step-by-step solution

The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The substances to which such an immune response is produced are called allergens.This could be because of the protected environment provided early in life.The immune system is designed to recognize and respond to foreign antigens, not to attack self-cells. Higher vertebrates can distinguish foreign molecules as well as foreign organisms, which is the basis for most experimental immunology. Auto-immune dis