CH 51 DEFENSE MECHANISMS OF THE BODY
51.2 Nonspecific (Innate) Immunity
1. Body Surface = Initial defence
2. Phagocytic Cells – nonspecific defence against pathogens
3. Inflammation is nonspecific response to infection/injury
4. Antimicrobial Proteins – interferons, complement proteins
Nonspecific immune defence is an inborn ability to protect against foreign cells/matter without having to recognize the invaders’
- Nonspecific defences recognize some general, conserved property marking the invader as foreign – particular classes of
carbohydrates/lipids in cell walls of microbes.
The Body Surface Represents an Initial Line of defence
- Very few microorganisms can penetrate the intact skin/body surfaces of most animals
o Ex. Tough, scaly skin of vertebrates, or rigid exoskeleton of arthropods.
- Glands on body surface secrete antimicrobial molecules – acids/enzymes like lysozyme – that destroy bacterial cell
- Mucus from respiratory/upper gastrointestinal tracts sticks microbes and prevent them from entering mucous
membrane barrier, so they’re swept into pharynx and swallowed or engulfed by cells.
Phagocytic Cells Provide Nonspecific Defence against pathogens that enter the body
- Phagocytes are cells capable of phagocytosis – type of endocytosis in which the cell engulfs particles and destroys
them by proteases or oxidizing agents (H O 2 2
- Found in body fluids – hemolymph and blood, and within tissues and organs
- Present in all classes of animals and are most fundamental and ancestral forms of body defences.
- In vertebrates, most phagocytes are leukocytes (white blood cells), which come from bone marrow.
o Ex. Leukocytes involve: neutrophils, eosinophils, monocytes, macrophages, and basophils.
- Neutrophils are the most abundant leukocytes found in blood and tissues, these engulf bacteria by endocytosis and
destroy them within vacuoles by proteases, oxidizing agents and antibacterial protein, defensins.
- Eosinophils are found in mucosal surfaces lining gastrointestinal, respiratory, and urinary tracts to prevent parasitic
- Monocytes circulate in blood after they become macrophages in all organs and tissues and they are large phagocytes
that engulf viruses and bacteria.
- Basophils secrete anticlotting factor heoparin to flush out infected site and histamine to attract infection-fighting cells. Feb/4/11
- Natural Killer (NK) cells are a leukocyte that participate in both non- and specific