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 kVirusescancerous cells
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 Our immune system
Nonspecific (innate) Specific (adaptive)
Speed: immediate/hours Effects after a few days(EX. when you get Measles
matter of inflammation, ex. you get cut in munites this vaccination, the immune system is activated only in 5
system is activated. it increases inflammation, dameged days) lots of activaties has to happen before B cells can
cells release chemicals which couses pain and swolling act
Leads to a state of immune memory, second time it is lot
No immunologic memory stronger
Specificity limited: One cell can recognize many Specificity improves during the course of response. One
pathogens (more or less from the same level) attack cell can recognize one pathogen. Highly diverse.
every thing many pathogens
Specific (adaptive) immunity: response to infection
EX. Hepatitis A and polio-adaptive immunity activated by asymptomatic disease.
infection: innate immunity, desease= recovery adaptive immunity are activated. EX. childhood deseases are activated
only once. if you get chicken box as child, next time you get this desease you do not get sick.
infection: innate immunity - no desease = adaptive immunity this case you do not need vaccination
vaccination -active adaptive immunity
Humoral Adaptive Immunity
Antigens (Ag) are substances (proteins, suger) that induce a specific immune response and subsequently react with the
products of a specific immune response
Antibodies (Ab, immunoglobulins, Ig) are protein molecules that are produced by plasma cells in response to an antigen
and can bing specifically to that antigen.
-can be used as an antigen exposure.
-interaction of antibodies.
-specificity is very important (can bind to influeza virus)- it is extremelly specific mollecule.
- Antigen binding site is unique and specific.
- free immunoglobulins
- y shaped with two heavy chains and 2 light chains
- have antigen-binding sites which complement epitopes found on the antigen
Antibodies recognize foreign pathogens and help destroy them
Neutralization occurs when antibodies bind to antigens ( ex antibody attaches to flaggela of bacteria and stops it from
moving or antibody will bind to the protein of virus and stop the virus)
Agglutination: forms a clump
-traps microbes and disposes by macrophages.
Percipiration: like agglutination but dissolved in fluid
Activation of complement
Response to a Infection
Infection --> innate immunity --> Disease --> Recovery --> Adaptive immunity -->Re-infected --> NO DISEASE
Functions of antibodies
An antibody molecule has 2 related functions in humoral immunity
i) Recognize and bind to certain antigen
ii) By binding to it, help counter its effect
Neutralization : Ab “ neturalizes” toxins bind to attachment molecules ( toxins in the blood can be stoped by bining
antibodies from attaching to where they are going) vaccination works in this area, tetunes for example vaccination can
stop this it from causing harm. Agglutination: creates complexes of cells
Precipitation: create complexes molecules
Complement activation occurs on antibody bound to pathogens
* the COM