Basic concepts in immunology
Basic Concepts in Immunology: Defense from Infections Disease
o We are covered in a cloud of microbes which help us more than harm us.
o They play defense
o Protect us from pathogens – simply by taking up space. Microbes protect us from autoimmune diseases
and allergic reactions.
- If you are covered by microbes on skin, gut, etc – other microbes (pathogens) will not have
space and will need to compete for space, food, etc.
o They boost the immune system –
o Research suggests that those with immune deficiencies will be treated by spores which will germinate in
their system and help immune system.Microbes protect us from auto-immune diseases and allergic
reactions. Animal- repopulate intestinal normal bacteria.
o In terms of allergies – those who are not exposed to other microbes as much as others, will likely develop more
allergic reactions than those who have had more exposure.
-Allergies and autoimmune disease are related to not having microbes
- The human body is home to millions of microbes and they form a protective web on our skin to protect us
Infectious Disease and Host Defense
>> Immunology is the study of our protection from and response to foreign invading organisms and altered host cells.
>> Note however that the our immune system is not that great at killing cancerous cellsViruses
In many cases activating the immune system is the only way to fight disease
o Our immune system can be manipulated – for example, smallpox was eradicated by giving vaccine which cause
-Synergism between antibiotics and the immune system
o Even if our immune system Is activated, antibiotics are given to help the body fight off the bacteria
Balance between infection and immunity
Infection: amount of pathogens, virulence
o Virulence is the characteristic of a microorganism in which that microorganism consistently causes disese.
Disease producing power!
o Virulence factors include a variety of mechanisms that microorganisms have evolved (ie. in the genes) to elude
and block host defenses or assist in host invasion.
Immunity : host defence mechanisms
Middle no disease
Infection and Immunity: Breaking the Balance
infection: amount of pathogens increase, virulence increase
immunity: host defense mechanisms stay the same or could decrease
what may decrease immunity: immunocompromised, "bubble boy" weak immune system, genetic diseases, and being
prone to infection.
immunity: host dense mechanisms increase (ie, allergy, autoimmune, acute inflammation -sepsis, chronic inflammation-
o Also known as an excessive immune response. It results from a increase in functional activity of the immune
o Excessive immune response disorders include: autoimmunity and hypersensitivity.
infection: amount of pathogens, virulence stay the same
Our Immune System- An Introduction
Three basic lines of defence
1) blocked by external barriers ex. skin
3) Immune system composed of T and B lymphocytes.
Anatomical and physicological barrlers
-Low stomach ph (not all bacterias can survive in stomach pH – H. Pylori)
-Ciliary clearance (oblet cells found in the mucous membrane of the lungs produce a sticky substance which traps
pathogens. Ciliary cells also part of the mucous membrane help with the movement of the mucus and trapped
pathogens, up and out of the lungs.)
- Smoking cigarettes destroys ciliary cells. Smokers are more prone to respiratory pathogens and consequently
respiratory infections (p.448).
-Lysome in tears and saliva - enzyme that destroys bacterial cell walls; and make them more susceptible to osmotic
pressures and digestion by phagocytes.-Intact skin (dry surface of skin does not promote growth of organisms
because moisture is preferred, constant shedding removes organisms)
-Intact skin - Sebum-an oily substance that helps keep skin intact by making it more pliable, and reduces the pH level on
the surface of the skin making the skin environment less favorable to certain bacteria.
-Coughing, sneezing and urinating also help to remove particles
Innate immunity ( pathogen activates this process)
Adaptive immunity (has memory with T &B cells, vaccines, can remember the bacteria that infected the body before)
-T and B cells
Intrinsic, Innate Immunity, Accquired Immunity
Normal Flora and Anatomical Barriers
-outer layer of intact skin ( has a lot of good and bad bacteria)
-normal flora (ex. yeast infection)
-flushing (sweat)- stopping from colonizing
- Sweat glands: secrete dermic dins/antimicrobial peptides- a broad-spectrum antimicrobial that acts against Gram-
positive and Gram-negative bacteria and fungi on the surface of the skin (p.447)
-Shedding of skin removes microorganisms
-fatty acids (can act like soap)
- Skin is slightly acidic
peristalsis- always moving bacteria can't colonize
low pH- prevents bacteria from surviving (H-pylori involved with peptic ulcer, trigger of cancer)
bile salts- act like soap
Nasopharynx and eye:
Mucus, saliva, tears, flushing (sneezing and coughing is a way of flushing organisms out of our body)
lysozyme – destroy bacterial cells ( it is an enzyme, which is from NAG and NAM and can be found in tears and saliva)
mucus prevents certain bacteria to bind