Infection and innate immunity

The innate immune response involves a variety of protective/effective mechanisms including:

• Epithelial barriers offering physical and mechanical barriers

• Chemical factors: in response to microbes, macrophages and other cells secrete cytokines that mediate many of the cellular reactions of innate immunity (i.e.: inflammatory cytokines  IL1, IL6, IL8, IL12, TNF-a). These activate vascular endothelium, lymphocytes, chemotactic factor & acute phase protein production. This causes chemoattraction of lymphocytes site of infections.

• Natural killer cells go to site of infection and kill intracellular microbes by killing the infected cell.

• Phagocytes such as: neutrophils, basophils, eosinophils, macrophages all play a role in recognising and ingesting microbes for intracellular killing.

• Complement pathway: these are membrane associated proteins (proteolytic enzymes) that play three major roles: 1) opsonisation (C3b), 2) breakdown products act as chemoattractants, 3) forms MAC that punches holes in microbial cell membrane.

These mechanisms provide an effective strategy against microbial infections, but they do not provide long last immunity nor memory. These mechanisms are immediate and control the infection while the adaptive response is being formed.

Category: Pathology Notes