Elements of the Immune System 03/25/2014
Immunology: study of mechanisms used to defend the body from invasion by organisms.
Infection caused by bacteria, viruses, and parasites.
Vaccination and Immunization: procedure where disease is prevented by prior exposure to the infectious
agent in a form that cannot cause disease.
First Used against Small Pox
Commensal Microorganisms Inhabit your body
500 microbial species live in the gut commensal species
Enhance nutrition (digestion and produce some proteins)
Protect against colonization by disease causing microorganisms
Example: E. coli secretes antibacterial proteins to stop other bacteria from colonizing the gut.
Antibiotic Treatments disrupt the natural ecology of the colon
Colonized by the largest number of commensal bacteria.
Antibiotics kill many of these commensal bacteria.
Pathogenic bacteria can gain a foothold and produce toxins that cause mucosal injury.
Red and white blood cells leak into gut between injured epithelial cells.
Four kinds of pathogen
Bacteria, Virus, Fungi, and parasites. Opportunistic pathogen: microbes that colonize body and cause illness when body defense are weakened
or in the “wrong” place.
Mechanical: Skin and Mucosal Surface form barriers against infection.
Epithelial cells joined by tight junctions
Flow of fluid: mucus, and saliva
Chemical: Sebum, acidity, enzymes, lysozymes.
Antimicrobial peptides defenses.
Biological: Normal human Flora.
Innate Immune Response: first primary response. Most infections are highly localized and controlled by the
innate immune response.
Pathogen recognition: system of soluble and cell surface proteins that identify pathogens.
Effector mechanisms: Elimination of pathogen
Cells that engulf bacteria, kill virus infected cells, or attack protozoa.
Complement proteins that mark and attack pathogens.
surface wound introduce bacteria which activates resident effector cells to secrete cytokines.
Vasodilation and increases vascular permeability allow fluid, proteins, and inflammatory cells to leave blood
and enter tissue.
The infected tissue becomes inflamed causing redness, heat, swelling, and pain.
Cytokines: soluble signaling proteins Vasodilation: dilation of local capillaries
Edema: swelling of cavities or tissues
Adaptive Immune Response adds to ongoing innate immune response.
If the innate immune response is overwhelmed: white blood cells, lymphocytes, are recruited to increase
the power of the innate immune response.
Is organized around an ongoing infection and adapts to the specific invading pathogen.
Innate vs Adaptive Immune Response
Innate Immune Response
Limited number of specificities
Constant during response
Necessary or death will occur
Cell Surface Receptors: Many types and non specific for single pathogen.