Lecture 2 Flashcards
What is immunity ?
- The protection against infectious disease granted either by the immune response generated by immunization or previous infection OR by other nonimmunologic factors
Basically… the body’s ability to resist infection from pathogens
Immunity can sometimes be ___________
unwated
Immunity can also be ____________, because it has ______________
trained, memory
What constitutes non-specific immunity ?
- Natural, innate – Meaning its ALWAYS THERE within us
- No memory, non-trainable
- Front line of defence, will be the first to try & protect us against any invader
Will always try to do the same thing first no matter the disease … If doesnt work you need specific immunity
What are the body defences that make part of non-specific immunity ?
- Skin
- Mucous membranes
- Iron-binding proteins
- Phagocytosis
- Complement
Skin - Non-specific Immunity
- Dry – Pathogens thrive in moist environments, cannot survive in most cases
- Acidic pH – Sebaceous secretions & sweat contain unsaturated fatty acids (bactericidal)
- Lower temp – Not ideal for some bacteria
Mucous Membranes - Non-specific Immunity
- Cilia of respiratory tract – Eliminate particles larger than 5 microns (eg. large bacteria carrying dust particles)
- Lysozymes – Antibacterial substance (eg. in tears)
- Acidic pH – gastric juice, vagina, urine
Iron-binding proteins - Non-specific Immunity
eg. transferrin, lactoferrin
Prevent bacterial growth as iron is a requirement for that in some bacteria
Phagocytosis - Non-specific Immunity
Polymorphonuclear WBCs, monocytes, & fixed macrophages in the tissues engulf and eventually destroy bacteria
Complement - Non-specific Immunity
- Set of circulating proteins in blood
- Opsonization – Binds to antibodies & makes whatever antibodies bound to more attractive for your immune system
- Membrane Attack Complex [ MAC ] – Able to recognize certain things on bacteria cell walls (eg. sugars) & can come together to form a pore → Allowing insides to leak out → Bacteria dies
What constitutes specific immunity ?
- Acquired, adaptive
- Directed against 1 particular species of microorganism and not any other
- Dependent on past exposure (vaccinations)
- Can be trained to increase strength
Mechanisms aimed at particular infecting organisms are divided into 2 major systems :
- Specific circulating antibodies in body fluids [ humoral immunity ]
- Cells trained to attack specific invading organisms [ cell mediated immunity ]
What are the immune cells ?
B cells – Make antibodies
T helper 1 & 2 cells – Mediators that signal which type of specific immune response we need to deploy (humoral / cell mediated)
- TH1 → Controls cell-mediated immunity
- TH2 → Controls humoural response
What is humoral immunity ?
The presence of circulating antibodies which are modified serum globulins tailored to react with particular chemical components of previously encountered invading organisms
Produced ONLY in response to these encounters
- EXTRACELLULAR PATHOGENS – Plays an important role in infections in which the pathogen produces toxins or has a capsule, as well as some viral infections
B cells are lights in a room, TH2 light switch
- TH2 cells turn on B cells via binding (tells it to start making more antibodies in response to the pathogen)
What are antibodies (Ab) ?
Referred to as immunoglobulin (Ig) , made in response to stimulation by an antigen & reacting specifically with it
Synthesized by B-lymphocytes / B-cells (plasma cells), production process requires antigen-presenting cells & T-helper 2 + T suppressor cells
- Able to distinguish foreign macromolecules (NON-SELF) from ‘normal’ body constituents (SELF)
- Recognize toxins, capsules & some viral proteins
- High specificity in combination with antigens
Antibodies : Constant vs Variable Region
Constant Region – Identical in all antibodies of the same isotype
- Determines mechanism used to destroy antigen
Variable Region – Responsible for antigen recognition, what actually BINDS to the antigen
- Each B cell makes a unique antibody that recognizes the antigen
What are the 5 classes of immunoglobulins ?
IgG, IgA, IgM, IgE & IgD
Which of the immunoglobins involved in defence mechanisms ?
IgG, IgA & IgM
IgG
- Basic unit found is a Y-shaped molecule
- Has 2 sites that combine specifically with the antigens, like a key in a lock
- The rest of the molecule can bind phagocytes and macrophages, which eventually destroy the microorganism
- Crosses placenta to later protect newborn
IgA
- Found in secretions (eg. mucosae of the respiratory, gastrointestinal & genito urinary tract, tears, milk, etc)
- Dimer : Made of 2 joined units of wide molecules to keep constant together
IgM
FIRST ANTIBODY THAT IS MADE + Main 1 produced in the early immune response
- Pentamer : Made of 5 units joined together
- Does NOT cross the placenta
IgE
- Involved in some hypersensitivity states
- Can lead to allergies if too many are made
- Defends against parasites
IgD
Role not completely understood
- VERY low levels in blood
- May have role in parasite function
What are antigens (Ag) ?
The chemical components which stimulate the production of antibodies which are then able to react specifically with those antigens
Capable of inducing a specific immune response - both humoral (production of Ab) & cell-mediated
Must be recognized by body as foreign (“non-self”) otherwise auto-immune disease can result
&
Antigenic structures in pathogen must be UNIQUE / not be found inside of you
- Usu protein, but can be glycoprotein, lipoprotein, polysaccharide
- Can be particulate or soluble
- Mol weight must be at least 10,000 to trigger an immune response
- Bacterial cells contain a number of antigenic molecules – Capsular substance, flagella, cell wall, etc.
Viruses usu have ______________ antigens
polypeptide
___ arms of the antibody bind to antigen
Y
Agglutinations
Antibodies can bind to another pathogen (of the same type) & clump it together
- Keeps pathogen localized / constrained so the body can efficiently get rid of it