first line defense - ANTIMICROBIAL SUBSTANCES

What substances protect the skin and mucous membranes from microorganisms?

Various substances like

• salty residue from sweat

• lysozyme

• peroxidase

• lactoferrin

• peptides

How does salty residue on the skin inhibit microbes?

Inhibits all but salt-tolerant microbes

What is the lysozyme function? Where is it found?

1. Degrades peptidoglycan

2. found in tears, saliva, muscus

3. found in body within phagocytic cells, blood, and fluid that bathes tissues

What role do Peroxidase play in defense against microbes?

Form antimicrobial compounds using hydrogen peroxide

Where are peroxidase system found?

• saliva

• milk

• body tissues

• phagocytes

How do micros with catalase enzyme resist peroxidase system?

Can convert hydrogen peroxide to water and oxygen, making them less susceptible to the lethal effects

What is the function of lactoferrin and transferrin?

Lactoferrin and transferrin are iron binding proteins, making iron unavailable to microorganisms and preventing their growth

• some can capture iron from host (making this useless)

Where are lactoferrin found?

Saliva, mucus, milk, and some phagocytes

Where are transferrin found?

Blood and tissue fluids.

What are antimicrobial peptides

SHort chains of amino acids (15-20) that have antimicrobial activity and produced many organisms.

What are the role of AMPs defensins

Protect the epithelial borders by inserting into microbial membranes forming pores and damaging the cells.

How do AMPs defensins protect body from microbial invasions?

Produced by certain epithelial cells and phagocytes where their expression increase during invasions.

How are defensins helpful for Phagocytes?

Help to destroy the microorganism they engulfed.

What is the relationship between vitamin D and AMP expression?

Vitamin D regulates the expression of some AMPs. Deficiency may increase susceptibility to cretan disease due to decreased AMP expression.