IMMUNOLOGY

Detailed explanation-1: -Skin, tears and mucus are part of the first line of defence in fighting infection. They help to protect us against invading pathogens. You have beneficial bacteria growing on your skin, in your bowel and other places in the body (such as the mouth and the gut) that stop other harmful bacteria from taking over.

Detailed explanation-2: -The immune system protects the body from possibly harmful substances by recognizing and responding to antigens. Antigens are substances (usually proteins) on the surface of cells, viruses, fungi, or bacteria.

Detailed explanation-3: -Nonspecific defenses include physical and chemical barriers, the inflammatory response, and interferons. Physical barriers include the intact skin and mucous membranes. These barriers are aided by various antimicrobial chemicals in tissue and fluids.

Detailed explanation-4: -Tears and mucus membranes would be a part of which defense system? innate external defenses (surface barriers) are the first line of defense and include tears, mucus membranes, and the skin.

Detailed explanation-5: -So, the correct answer is ‘Killer T-cells’.