AP BIOLOGY

Detailed explanation-1: -Expert-Verified Answer. Explanation: An Antigen is any FOREIGN substance that can enters the body stimulating an immune response. It includes toxins, proteins etc, and can get into the body through ANY openings.

Detailed explanation-2: -An antigen is a foreign substance that enters your body. This can include bacteria, viruses, fungi, allergens, venom and other various toxins. An antibody is a protein produced by your immune system to attack and fight off these antigens.

Detailed explanation-3: -A macrophage is the first cell to recognize and engulf foreign substances (antigens). Macrophages break down these substances and present the smaller proteins to the T lymphocytes.

Detailed explanation-4: -Innate immunity: Everyone is born with innate (or natural) immunity, a type of general protection. For example, the skin acts as a barrier to block germs from entering the body. And the immune system recognizes when certain invaders are foreign and could be dangerous.

Detailed explanation-5: -IgG antibodies are usually of higher affinity and are found in blood and in extracellular fluid, where they can neutralize toxins, viruses, and bacteria, opsonize them for phagocytosis, and activate the complement system.