PATHOLOGY

Detailed explanation-1: -Nonspecific defenses include anatomic barriers, inhibitors, phagocytosis, fever, inflammation, and IFN.

Detailed explanation-2: -(D) Killer T-cells – They are a part of acquired immunity. They are involved in the body’s third line of defence. And, hence they are not a part of non-specific defence.

Detailed explanation-3: -The first line of defense against infection are the surface barriers that prevent the entry of pathogens into the body. The second line of defense are the non-specific phagocytes and other internal mechanisms that comprise innate immunity.

Detailed explanation-4: -The innate immune system acts as the first line of defense, sensing the virus through pattern recognition receptors and activating inflammatory pathways that promote viral clearance.