Bio 2730 Chapter 14 - Innate Immune Response

Innate immunity

routine protection present at birth; it is germ-line encoded meaning that it is passed from one generation to the next, an includes anatomical barriers as well as certain cell types and chemicals

Complement system

detects microbial cells and antibodies bound to antigens, and is activated in response

Cytokines

"voices" of the cell; produced by one cell diffuses to another and binds to the appropriate cytokine receptor of that cell

Inflammatory response

the body's. attempt to contain a site of damage, localize he response, eliminate the invader, and restore tissue function.

Hematopoiesis

the formation and development of blood cells

Erythrocytes

red blood cells

Leukocytes

white blood cells

Granulocytes

contain cytoplasmic granules filled with various compounds important for the cells' protective functions

Lymphocytes

responsible for adaptive immunity

Neutrophils

efficiently engulf and destroy bacteria and other material

Dendritic cells

sentinel cells that function as "scouts"

Macrophage

a differentiated form of monocyte; they have gained specialized properties

Adhesion molecules

on the surface of cells that allow those cells to "grab" other cells

Membrane Attack Complex (MAC)

complexes of complement system proteins spontaneously assemble in cell membranes, forming this doughnut-shaped structure

Opsonin

phagocytes that have receptors that attach specifically to molecules

opsonization

"prepared for eating"

Pattern Recognition Receptors (PRRs)

sensors that allow the body's cells to "see" signs of microbial invasion

Pathogen-associated molecular patterns (PAMPs)

also known as microbe-associated molecular patterns (MAMPs); detect certain groups of microbes

Phagocyte

specialize in engulfing and digesting microbes and cell debris

Phagocytosis

the process of how phagocytes engulf and digest the material, including invading microbes

Diapedesis

a process in which cells squeeze between the dilated vessel walls

Acute

inflammation short-term inflammatory response

Apoptosis

programmed cell death that does not trigger an inflammatory response

Pyroptosis

programmed self-destruction that triggers an inflammatory response

Know the three types of first line defenses and why they work.

- Physical barriers

o These borders separate the interior of the body from the surrounding environment

- Antimicrobial substances

o Skin and mucous membranes are protected by a variety of substances that inhibit or kill microorganisms

- Normal microbiota

o The population of microorganisms that routinely grow on the body surface of healthy humans

o Essential to the development of the immune system; the system learns to distinguish harmless ones from pathogens

Know two ways the epithelial barriers help remove bacteria and other microbes from the body.

- Peristalsis - the rhythmic contractions of the intestinal tract that propel food and liquid and remove bacteria

- Mucociliary escalator - moving layer of mucus and cilia lining the respiratory tract that traps bacteria and other particles and moves them into the throat

Know the four listed antimicrobial substances listed in Figure 14.4 and what they do.

- Lysozyme - an enzyme that degrades peptidoglycan

- Peroxidase enzyme - part of systems that form antimicrobial compounds, using hydrogen peroxide in the process

- Lactoferrin - an iron-binding protein

- Defensin - a group of Antimicrobial peptides (AMPs)

Know what normal microflora is

The population of microorganisms that routinely grow on the body surfaces of healthy humans

Granulocytes

o Eosinophil - important in ridding the body of parasitic worms; release chemicals to destroy eukaryotic parasites; found mainly in tissues below the mucous membranes

o Basophil - involved in allergic reactions and inflammation; release histamine and other inflammation-inducing chemicals; found in blood, whereas mast cells are present in most tissues

o Neutrophil - efficiently engulf and destroy bacteria and other material; phagocytosis; they also release substances that trap and destroy microbial invaders; most abundant in blood

Lymphocytes

o Natural killer (NK) cell - kills certain types of cells

o T cell & B cell- specific in the mechanism of antigen recognition; participate in the adaptive responses; found in lymphoid organs; also in blood

Chemokines

o Source - various cells

o Effect - chemotaxis

Interleukins IL-1

• Source - Macrophages, epithelial cells

• Effect - T cell activation; macrophage activation; induces fever

Interleukins IL-2

• Source - T cells

• Effect - T cell proliferation

Interleukins IL-4

• Source - T cells, mast cells

• Effect - Promotes antibody responses

Interleukins IL-6

• Source - T lymphocytes, macrophages

• Effect - T- and B-cell growth; inflammatory response; fever

Interferons

o Source - Various cells

o Effect - Regulate immune responses; antiviral

Tumor Necrosis Factor (TNF)

o Source - Macrophages, T cells, NK cells

o Effect - promotes inflammation; cytotoxic for some tumor cells; regulates certain immune functions

Toll-like Receptors (TLRs)

found in macrophages, dendritic cells, and in sterile body sites; they detect molecules that are specific to bacteria (peptidoglycan, LPS, flagellin)

NOD-like Receptors (NLRs)

cytoplasmic receptors that detect cell damage or traces of bacterial products that can produce signaling and other reactions like degranulation.

RIG-like Receptors (RLRs)

cytoplasmic receptors that detect viral RNA; detection results in the production of interferon.

Know the six steps of phagocytosis and their order.

1. Chemotaxis - phagocytic cells are recruited to the site of infection or tissue damage by chemicals that act as chemoattractants

2. Recognition and Attachment - phagocytic cells use various receptors to bind invading microbes either directly or indirectly

3. Engulfment - once the phagocyte has attached to a particle, it sends out pseudopods that surround and engulf the material

4. Phagosome Maturation and Phagolysosome Formation - a phagosome has no antimicrobial capabilities, but it matures to develop these; the maturation stages are highly regulated, and depend on the type of material ingested

5. Destruction and Digestion - Various enzymes contributed by the lysosomes degrade peptidoglycan and other components. Antimicrobial peptides damage membranes of the invader and lactoferrin binds iron

6. Exocytosis - phagolysosome releases undigested debris to the outside of the cell by fusing with the phagocyte's cytoplasmic membrane

Know the roles of macrophages and neutrophils and how they are different (in basic terms).

- Macrophages - hardy and can live extended periods of time and many attacks; act as sentinels and minor skirmishers

- Neutrophils - kamikaze-fighters, life span limited to a few hours after recruitment from blood; heavy fighters

Know the four-point purpose of inflammation.

- Contain the site of damage

- Localize the response

- Eliminate the invader

- Restore tissue formation

Know the four cardinal signs of inflammation.

Redness, swelling, heat, pain

Understand the general steps involving resident macrophages and neutrophils in handling a minor injury.

- Normal blood flow in the tissues as the injury occurs

- Neutrophils are the first phagocytes recruited to the site

- As the infection is brought under control, macrophage ingest dead cells and debris

- Inflammatory mediators cause small blood vessels to dilate. The phagocytic cells tumble to halt and squeeze between the endothelial cells and enter the tissue