Question

Select the correctly described examples of host defense mechanisms.

Answer 1

Ans: Host defence mechanism-

- Inate host defence due to B and T cells and their products.

Host defence mechanism are composed of two systems:

(1) innate (nonspecific) defenses, which in general defence against microorganisms ; and

(2) adaptive (specific) immunity, which defence against a particular microorganism.

Innate defenses were classified into 3 major categories:

(1) physical barriers (intact skin and mucous membranes); (2) phagocytic cells (neutrophils, macrophages, and natural killer cells); and (3) proteins (lysozyme, and interferon). Antibodies and T lymphocytes mediate adaptive immunity.

Bacteria enter skin Activation of complement via alternative pathway Phagocytosis by Neutrophils Macrophages C5a attracts neutrophils C3b opsonizes bacteria, which enhances phagocytosis by neutrophils C5,6,7,8,9 form membrane attack complex that lyses bacteria Cytokine production Present epitopes and stimulate Tumor necrosis factor induces inflammation Interleukin-1 induces fever Interleukin-6 induces acute- phase proteins Chemokines (e.g., IL-8, MIP) attract neutrophils and macrophages Antibody- mediated immunity Cell- mediated immunity