IMMUNOLOGY

Detailed explanation-1: -The innate immune system provides the first line of defense, which is divided broadly into two categories – physical/chemical barriers and nonspecific resistance.

Detailed explanation-2: -The second line of defense is nonspecific resistance that destroys invaders in a generalized way without targeting specific individuals: Phagocytic cells ingest and destroy all microbes that pass into body tissues. For example macrophages are cells derived from monocytes (a type of white blood cell).

Detailed explanation-3: -The first line of defence is your innate immune system. Level one of this system consists of physical barriers like your skin and the mucosal lining in your respiratory tract. The tears, sweat, saliva and mucous produced by the skin and mucosal lining are part of that physical barrier, too.

Detailed explanation-4: -The correct answer is option b. Innate immune responses represent the first line of defense against invading pathogens because the innate immune response provides general protection against a wide variety of pathogens through antimicrobial peptides, mucous and skin barriers, complement antibodies, etc.

Detailed explanation-5: -Anatomical and physiological barriers provide the crucial first line of defense against pathogens. These barriers include intact skin, vigorous mucociliary clearance mechanisms, low stomach pH and bacteriolytic lysozyme in tears, saliva and other secretions.