L11 - Innate Immunity and Host Defenses

Flashcards covering the mechanisms of innate immunity, including physical/chemical barriers, types of leukocytes, the inflammatory response, and nutritional immunity as described in the lecture notes.

Innate Immunity

Non-specific control of infection that includes the first and second lines of defense.

First line of defense

A surface protection composed of anatomical and physiological barriers that keep microbes from penetrating sterile body compartments.

Second line of defense

A cellular and chemical system that comes immediately into play if infectious agents make it past the surface defenses.

Third line of defense

Specific host defenses that must be developed uniquely for each microbe through the action of specialized white blood cells like B cells and T cells.

Lysozyme

An enzyme found in tears and saliva that hydrolyzes peptidoglycan in the cell walls of bacteria.

Neutrophils (PMNs)

Phagocytes in blood that comprise $40-70\%$ of circulating WBCs, active in large numbers to engulf and kill bacteria using toxic chemicals.

Basophils

White blood cells that function in inflammatory events and are similar to mast cells.

Eosinophils

White blood cells active in worm and fungal infections, allergy, and inflammatory reactions.

Monocytes

Blood phagocytes that rapidly leave the circulation and mature into macrophages and dendritic cells.

Macrophages

The largest phagocytes that ingest and kill foreign cells; they act as resident and patrolling "big eaters" in tissues.

Dendritic cells

Relatives of macrophages that reside in tissues and the mononuclear phagocyte system, responsible for processing foreign matter and presenting it to lymphocytes.

Natural killer (NK) cells

Cells related to T cells but displaying no antigen specificity, active against cancerous and virally infected cells.

PAMPs

Pathogen-associated molecular patterns; signal molecules on the surfaces of microbes (such as peptidoglycan, lipopolysaccharide, or double-stranded RNA) that are not present in mammals.

PRRs

Pattern Recognition Receptors; receptors on host immune cells that bind to Pathogen-associated molecular patterns (PAMPs).

NETs

Neutrophil Extracellular Traps; the release of chromosomes by neutrophils to entangle invading organisms.

Cytokines

Molecular messengers that allow cells to talk with one another via autocrine, paracrine, or endocrine signaling.

Chemokines

Specific signaling molecules that initiate chemotaxis, used by cells to find the site of infection.

Rubor

Redness caused by increased circulation and vasodilation in injured tissues during the inflammatory response.

Calor

Warmth resulting from the increased flow of blood to a site of injury.

Tumor

Swelling caused by increased fluid escaping from tissues during inflammation.

Dolor

Pain caused by the stimulation of nerve endings during the inflammatory response.

Complement

A protein cascade that targets bacterial membranes to cause lysis and signals macrophage chemotaxis and activation.

Interferon

A chemical released by virus-infected cells that signals neighboring cells to turn on anti-viral systems; the reason you feel horrible when you have a viral infection

Lactoferrin

A host iron-binding protein found in milk, blood, tears, and saliva.

Calprotectin

A host zinc-binding protein found in most cell types and compartments.

Siderophores

Counter-mechanisms used by bacteria to obtain iron from the host's iron-sequestering proteins.