• Bacterial/fungal -- antibiotics, nucleases
• Plants -- the hypersensitive response causes apoptosis (programmed cell death) leading to an oxidative burst -- peroxides directly attack pathogens and also increase the rigidity of cell walls in surrounding, living cells
• Animals – physical/chemical barriers and the immune system (innate, adaptive)

• Skin: Dry (keratin), low pH, high salt (sweat)
• Respiratory tract: Nose filtration of particles
• Mucous membranes: Mucin (protein) + glycoproteins form mucus that coats mucosal surfaces
• Flow of liquids (mucous, saliva, urine, tears)
• Mucociliary movement by ciliated columnar cells (respiratory tract, genitourinary tract)
• Peristalsis (nonciliated columnar cells of GI tract)

• HCl produced by parietal cells of stomach (low pH)
• Leukocytes produce lysozyme, peroxidase, and lactoferrin/transferrin (iron chelator)
• Defensins and histatins are antimicrobial peptides secreted by neutrophils and natural killer cells that damage bacterial cell walls
• Liver produces bile acids (antimicrobial)
• Gut flora--this is one of the main examples of how normal flora can prevent the colonization/overgrowth of other “bad” organisms

• T helper cells direct T cells and B cells
• T&B cells = lymphocytes that have receptors for many antigens.
• Effector B cells produce antibodies and can become dormant memory cells which produce more Ab when it sees the antigen again.
• Cytotoxic T cells kill tumor cells or cells that have been invaded by a pathogen.
• Antibodies produced by B cells aid the immune system by tagging cells that have become infected with a pathogen. Once a cell has been labeled they are essentially marked for destruction and are destroyed by phagocytes, neutrophils, mast cells…
• Upon antigen recognition, Dendritic cells migrate to the lymph nodes to present Antigens to T cells and initiate proliferation

Hallmarks of inflammation:

-Swelling due to plasma leakage into tissues

-Redness and heat due to increased blood flow through dilated vessels

-Pain due to increased fluid in tissues and effect of chemicals on sensory nerve endings

Problems of inflammation:

-Can cause massive tissue damage

-Systemic shock

Produced by lymphocytes (B cells)

Very specific, strong binding

Chains held together by disulfide bonds

Bind to “invading” molecules, targeting them for destruction

Interaction of the antibody with an antigen causes a change in shape of the antibody

The variable regions are the receptors for antigen binding

This interaction activates the complement system (opsonization) and the effector cells (T helper cells, cytotoxic T lymphocytes)

• Rod-shaped, gram-negative, motile enterobacteria

• Serovar – Organism classed together based on their surface antigens

• Salmonella genus is highly diverse, with over 4400 different kinds of serovar groups

• Surface antigens are also important in recognizing “self”

• Hens that are raised to produce eggs become infected with the bacteria

• Colonizes intestinal tract, liver, spleen, and ovaries of infected chickens

• Passes from ovaries to eggs

• Also picks up Salmonella from excrement as it passes through the cloacae

• Symptoms include dehydration, fever, abdominal cramps, and diarrhea

• Rarely fatal except in infants, elderly, and immunocompromised patients

• Results in dehydration, which can be lethal

• Occurs 8-72 hours after infection

• Lasts 4-7 days

• 75% of these cases are due to comsumption of contaminated eggs

• Second only to Campylobacter as cause of bacterial diarrheal illness

• Enzyme Linked Immuno-Sorbent Assay
• Detects the presence of antigens with special, lab-created antibodies linked to enzymes that, in the presence of a chromogenic reagent, produce color or fluorescence that can be measured quantitatively.
• Very specific, very sensitive assay

1) Antigen (lipopolysaccharide) is affixed to the bottom of the well (in our case a 96-well plate)

2) Egg yolk is added to the well; if antibodies specific for the antigens are present, they will bind. • Note: Antibodies outside their host behave slightly differently, and exhibit some non-specific binding • In order to prevent this, we “block” non-specific binding sites with detergents (tween) and proteins (milk) which helps the antibody bind to the specific site

3) Rinse (wash); only bound antibodies remain.

4) Add anti-chicken antibody antibodies coupled to enzyme; rinse to remove unbound antibodies.

5) Add chromogenic reagent; reagent is cleaved by enzyme, resulting in signal proportional to the amount of bound antibody- can get a quantity