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Surface barriers, inflammation, and immune response

What are the 3 host defense mechanisms?

Surface barriers

What is the first line of defense?

The first line of defense includes...

Epidermis and mucosa, secretions (mucus, saliva, lacrimal, etc.), and normal microbiota on the skin and mucosa

The epidermis and mucosa are...

A good barrier when intact and have ciliated cells (lower respiratory)

Normal microbiota on skin and mucosa...

Colonize niches; out-compete pathogens, disease may result if killed (antibiotics, etc.)


What is the second line of defense?

The second line of defense includes...

Inflammatory mediators (bradykinin, histamine, etc.) and complement

Inflammatory mediators...

Alter blood flow, capillary permeability, etc., and attract phagocytic WBC's by chemotaxis

PMN's (neutrophils) come...

First, eat MO's, and release enzymes

Macrophages come...

Later, efficient killers and eaters, release toxic forms of oxygen (NO, nitric oxide), produce interleukins (IL); enhance response


Serum proteins that can become activated; help immune system destroy invaders

The Immune Response

What is the third line of defense?

Antigens (from MO) stimulate...

lymphocytes (B cells and T cells

B Cells

Produce plasma cells and make antibodies


Proteins that bind to antigens


Circulates in blood; Attaches to bacteria, viruses and Inactivates toxins


In secretions


Clumps antigens together

T Cells

Cell-mediated response (cell-to-cell contact), Kills MO's and regulate immune response, Remove abnormal or virus-infected cells

Immunization (Vaccination)

Antigens are injected; MO's (weakened or dead), components, neutralize toxins; Stimulates immune response (B cells, T cells, and memory cells)

Memory Cells

Confer immunity (future)

DPT (Diptheria, Pertussis, Tetanus)

Contains cells fragments from Bordetella pertussisi and toxoids made from Diptheria and Tetanus exotoxins


Inactivated by heat, formaldehyde, etc.; Still antigenic: body produces antitoxins (antibodies) against them

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