Chapter 14 Innate Immunology

First Line of Defense

Skin, Mucous Membranes, Chemical Conditions, Enzymes, Antimicrobial Peptides

First Line of Defense: Skin

Epidermis and Dermis

Skin: Epidermis

Keratin (outer layer) is constantly shed off

Sweat glands: Chemicals, salt

Oil Glands: sebum - acidic

Skin: Dermis

Middle Layer of skin

Contains phagocytes

Mucous Membranes

thin epithelial layer

more permeable than skin and sheds constantly

Mucous Membrane: Mucus

2 layers - outer and inner

movement constantly so it prevents attachment

chemicals

Mucous Membrane: Cilia

Hair-like structures

movement

prevent attachment

Chemical Conditions

low pH (stomach acid, skin, sebum), salt (sweat), low moisture (skin)

Enzyme

Lysozyme in tears and saliva digests peptidoglycan

Antimicrobial Peptides

Non-specific

Mechanism: insert into membranes, form pores; disrupt internal signaling/enzymes; unknown

Second Line of Defense:

“Barrier Breach”: complement (soluble, free floating)

Innate Immune System

Present at birth

Responds immediately - Provides a rapid host reaction

Prevent microbial access (prevent spread w/in body)

Eliminate the threat - 80%

Call for reinforcements

More innate cells or adaptive cells

Activate the adaptive immune response

Complement

highly conserved evolutionarily

Humans: These proteins are constantly produced by the liver

Complement Cascade

Complement Cascade

One complement protein activates others, and so on

Granulocytes

Neutrophils (60-70%) and Eosinophils (2-4%)

Neutrophil

Short-lived but rapidly replaced by bone marrow

Extravasation (recruited from blood into tissue)

Patrol blood, lymphoid tissue, and other tissue

Functions of Neutrophil

Phagocytosis

Inflammatory mediators (secrete), recruit other immune cells, kill degranulate (toxic, ROS), NETS

Agranulocytes

Macrophages, Dendritic Cells, Lymphocytes (adaptive) (20-25%)

Macrophages

Guard the barriers (skin and mucosal membranes) by constantly “sampling” the environment

Usually the first on scene since they are already in tissue

Functions of Macrophages

Phagocytosis

Inflammatory mediators )secrete), recruit, and activate other immune cells