MICRO 402 Chapter 31 Host Resistance

What is an antigen?

Large macromolecules with complexity (something that is recognized by the immune system)

Innate arms of the immune system

1st line of defense, present at birth, lacks memory, generalized/immediate response

adaptive arms of the immune system

Reaction to specific antigens, has memory, primary response takes weeks

Physical barriers — skin

Contains pH and temperature, keratinocytes (produce oil and are tightly packed), Langerhans (skin immune cells)

Physical barriers — mucous membranes

Epithelial cells line the tract to trap, destroy, and restrict bacteria

Goblet cells

Produce mucus

Paneth cells

Secrete lysozyme and antibacterial peptides

Chemical barriers — lysozyme

Found in tears, secretions of the mucous membrane, and breast milk (hydrolyzes the glycosidic bond between NAG and NAM)

Chemical barriers — lactoferrin

Sequesters free iron

Chemical barriers — Lactoperoxidase

Enzymes produce superoxide radicals and reactive oxygen species

Chemical barriers — the complement system

20+ proteins circulating in the blood (inactive form) and produced by the liver

C3 degrades into…

C3a and C3b

Gram-negative bacteria present C3b binds to…

LPS

C3a diffuses and recruits…

WBC

C5b deposits on the bacterial outer membrane…

Forms membrane attack complex (MAC)

Granulocytes

Irregularly shaped nuclei with two to five lobes and are reactive with substances that kill microbes

Neutrophils

A major phagocyte of the cell (reactive with oxygen species and short lifespan)

Antigen presenting cells (APCs)

Macrophages are present (directly kill invaders) and dendritic cells (in skin and mucous membrane)