LIFE SCIENCE

Detailed explanation-1: -The immune system recognizes invaders by their antigens, which are proteins on the surface of the invading cells (see Figure 1).

Detailed explanation-2: -That is, the immune system must be able to distinguish what is nonself (foreign) from what is self. The immune system can make this distinction because all cells have identification molecules (antigens) on their surface. Microorganisms are recognized because the identification molecules on their surface are foreign.

Detailed explanation-3: -So Why Doesn’t It? The immune system can clearly recognize cancer cells as different, yet often it is unable to stop them from growing.

Detailed explanation-4: -They do this by recognising substances called antigens on the surface of the microbe, or in the chemicals they produce, which mark the microbe or toxin as being foreign. The antibodies then mark these antigens for destruction. There are many cells, proteins and chemicals involved in this attack.