BIOL 203 LCC, Microbiology (Exam 5) (Innate immune system)

How do microbes cause disease?

1) Gain entry to the host

2) Attach to and invade specific cells and/or tissues within the host

3) Survive host immune system defenses

first layer of defense

external physical barriers and their associated chemical barriers. (skin and mucous membranes)

second layer of defense

cellular defense, inflammation, fever, and molecular defense like complement and interferon.

third layer of defense

lymphocytes (B and T cells)

Innate

layers 1 & 2

act against any type of invading agent

The first line of defense

not specific

Adaptive

Layer 3

specific

involves action of B and T Lymphocytes

Six main Innate defenses

1) Physical barriers

2) Chemical barriers

3) Cellular defenses

4) Inflammation

5) Fever

6) Molecular defense

Layer 1 defenses

Physical barriers and Chemical barriers

Physical barriers

skin and mucous membranes

Chemical barriers

sweat, sebum, pH, lysozyme, defensins, transferrin, and lactoferrin

what does our body do following a failure or breach of physical barriers (layer 1)?

must depend on layer 2

Layer 2 defenses

Cellular defenses, inflammation, fever, and molecular defenses

Homeopoiesis

production of blood cells

stem cells

undifferentiated cells, precursor of new blood cells

Leukocytes

white blood cells; granulocytes and agranulocytes

Granulocytes

lobed nucleus, often presence of granules in cytoplasm

Neutrophils, eosinophils, basophils

Agranulocytes

unlobed, rounded nucleus

Neutrophils

55-90% - phagocytes and first responders to site of infection

Eosinophils

1-3% - orange granules and bilobed nucleus; destroy eukaryotic pathogens

Basophils

0.5%-mobile in the bloodstream, release potent chemical mediators (histamine)

Mast cells

similar to basophils but nonmobile found bound to connective tissue

Lymphocytes

20-35%, specific immune response

B cells

when activated, produce antibodies

T cells

when activated, modulate immune functions and kill foreign cells

Monocytes/Macrophages

3-7% - largest of WBCs, kidney-shaped nucleus; phagocytic

Macrophages

final differentiation of monocytes

dendritic cells

trap pathogens and participate in immune reactions

Erythrocytes

develop from bone marrow stem cells, lose nucleus, simple biconcave sacs of hemoglobin

Platelets

formed elements in circulating blood that are not whole cells

Phagocytes

cells that engulf and destroy bacteria

Phagocytosis

1) Chemotaxis

2) Adhere

3) Ingest MO

4) Digest MO

Chemotaxis

Cell movement that occurs in response to chemical stimulus

What are PAMPs?

molecules found on groups of microbes

Natural Killer

cells secrete products that trigger death of virus-infected cells and certain cancers

lymphatic system functions

-Collect excess fluid from spaces between body cells

-Provide many innate and adaptive defense mechanisms against infection

-Transport digested fats to cardiovascular system/bloodstream

Spleen

can filter blood and recycle red blood cells

Thymus

educates T-cells

Lymph nodes

encapsulated globular structures that act as filters an via defensive cells present clear the lymph of MO

Tonsils

aggregation of lymphocytes

Signs of infammation

redness, warmth, swelling, pain

Diapedesis

process by which white blood cells migrate from the blood vessels to the site of infection

molecular defenses

interferon and complement

Interferon

Proteins that act nonspecifically to cause cell killing or to stimulate cells to produce antiviral proteins

Complement

26 proteins that work in concert to destroy bacteria and viruses

Pathways for Complement Activation

-classical

-lectin pathway

-alternative

Classical

activated by the presence of antibody bound to MO

lectin pathway

nonspecific reaction of a host serum protein that binds mannan

Alternative

begins when complement proteins bind to normal cell wall and surface components or MO

4 stages of complement cascade

1. Initiation

2. Amplification and cascade

3. Polymerization

4. Membrane attack

Opsonization

antibodies bind to antigens on bacteria creating a target for macrophages or neutrophils, triggering phagocytosis

inflammation

initiates and enhances inflammation by stimulation chemotaxis and phagocytosis, also adhere to basophil and mast cells to induce histamine release to increase permeability of blood vessels

membrane attack complex

a membrane pore protein made in the complement cascade