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

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

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 .

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

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

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

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.

The Classical pathway

Alternative pathway

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