Lecture 8 — Innate Immunity

Present from birth.

Innate immunity and adaptive immunity.

It is rapid, always available, and relatively nonspecific.

It recognizes common features shared by groups of pathogens rather than one specific pathogen.

Normal microbiota, physical barriers, chemical defenses, and cellular defenses.

They compete with pathogens and make it harder for them to colonize the body.

They consume nutrients that pathogens would otherwise use.

They occupy surfaces where pathogens might otherwise attach.

They can produce acids or antimicrobial substances that inhibit or kill other microbes.

Pathogens such as *Clostridioides difficile* may overgrow.

It can colonize the intestine and produce toxins that damage the intestinal lining.

Inflammation of the colon that can occur when antibiotics disrupt normal microbiota and allow *C. difficile* to overgrow.

It acts as a physical barrier that prevents microbes from entering the body.

It traps microbes and helps remove them from body surfaces.

An antimicrobial enzyme that damages bacterial cell walls.

Small proteins that can damage or inhibit microorganisms.

The process by which a cell engulfs and digests particles or microorganisms.

Cells that engulf and destroy microbes by phagocytosis.

Neutrophils and macrophages.

A nonspecific response to tissue damage or infection.

Redness, heat, swelling, and pain.

Inflammatory mediators such as histamine.

Widening of blood vessels, which increases blood flow to an area.

To allow fluid and immune components to move from the blood into affected tissues.

Directed movement of cells toward a chemical signal.

It attracts immune cells toward the site where pathogens are present.

Immune cells that release inflammatory mediators such as histamine.

A group of blood proteins that activate in a cascade to help eliminate pathogens.

A sequence in which activation of one protein leads to activation of additional proteins.

Inflammation, chemotaxis, opsonization, and direct microbial killing.

Coating a pathogen to make it easier for phagocytes to recognize and engulf.

A group of complement proteins that forms a pore in a target membrane.

It creates holes in their membranes, disrupting membrane function.

Activation of complement protein C3.

Classical, alternative, and lectin pathways.

Antibodies bound to antigens on a pathogen.

It uses antibodies produced by the adaptive immune system to activate complement.

Complement activation on microbial surfaces without requiring antibodies.

Binding of mannose-binding lectin to certain sugars on microbial surfaces.

It helps opsonize pathogens and promotes further complement activation.

Inflammation and recruitment of immune cells.

To damage susceptible pathogen membranes by forming pores.