1. Nonspecific (Innate) Host Resistance
Chapter 31
Nonspecific (Innate) Host Resistance

2. Nonspecific defenses of the host
These defense work against all types of microbes

3. First line of defense – skin, mucous membrane and their secretions.
Skin – closely packed cells
Mucous membrane – mucus – traps bacteria
Gastric juice – hydrochloric acid
Tears, saliva, mucus – lysozyme .

4. Second line of defense – phagocytosis, inflammation, antimicrobial substances.
White bood cells
Granulocytes
Neutrophils – active during the initial stage of the infection – phagocytic
Eosinophils – phagocytic
Number of cells increases during protozoan and helminthic infestations

5. Basophils - histamine
Monocytes – they transform into macrophages in the tissue.
Macrophages are phagocytic – active during the later stages of the infection.
Lymphocytes - immunity

7. Inflammation Response to tissue injury Redness, pain, swelling
Caused by chemicals. Sharp objects, bacteria
Histamine – mast cells in the connective tissue, basophils – vasodilation.
Leukotrienes – mast cells, basophils – increases vascular permeability

9. Complement system Serum proteins ( 20 different)
System can be activated by classical pathway and alternative pathway.
The system kills bacteria
It also causes inflammation, enhances phagocytosis.

10. The Classical pathway

11. Alternative pathway

13. Interferon
Prevents the spread of the virus from the infected host cells to other cells in the area.