Microbiology Final Flashcards
What is an antigen?
Stimulates an immune response: A substance the body recognizes as forign
Non-self
immunogenic - stimulates an immune response (immunogen)
large, complex molecules
Composed of antigenic determinants - the part of the antigen that actually stimulates and reacts with the immune response
What parts of the bacteria have antigenic determinants?
Proteins, lipids, mucleic acids, CHO
Flagellum
Pilli
**Proteins make the best antigenic determinant
What is a hapten?
molecule that, by itself, is too small to be immunogenic
**When attached to a larger molecule like a protein then it can be imunogenic
Properties of immune responses
Recognition - of self vs. non-self
- self = host tissue
- Non-self = forign substances
Specificity - each immune response is directed toward a specific ag but the response to one ag doesn’t affect the response to another. Cross Rx occurs if two ag’s are similar
Diversity - The immune system can respond to many different Ag’s (>1 billion)
Memory - The immune system can recognize ag’s it has previously encountered. It responds quicker the second/subsequent time it encounters that ag
Define tolerance
the host doesn’t mount an immune response to self ag’s under normal circumstances
B lymphocytes (B cells)
Arise in bone marrow; primarily involved in antibody mediated immunity
Reside in the lympohid organs and in the bloodstream
Receptor: an Ab molecule that recognizes and binds a specific Ag
T lymphocytes (T cells)
Arise in thymus gland; Primarily involved in cell-mediated immunity
Reside in lymphoid organs and in the bloodstream
Receptor: T-cell receptor, receptor that recognizes and binds a specific Ag.
Cell-mediated Immune Response
- Ag is recognized and phagocytosed by macrophages- Ag presenting cells
- Macrophages fins corresponding helper T cell; presents Ag (binds)
- Helper T cells sound the alarm (CD-4+) - interleukin-1 stimulate T-cells to mature; interleukin-2 stimulates T-cells to rapidly divide
- The alarm encourages the production and rapid division of cytotoxic T-cells
- Cytotoxic T-cells find and infect cells that present Ag and lyse them
What are cytokines?
Cell communication molecules; released by one cell to signal or stimulate another cell.
Released by helper T cells
What are perforins?
Released from cytotoxic T cells; forms pores in target cell membrane
What are Antibodies?
Proteins that circulate in the bloodstream
sythesize and secreted by plasma cells
Each Ab is specific for 1 particular antigenic determinant
React with Ag that is outside host cell like toxins, bacterial surfaces, viruses
Plasma cells
B lymphocytes that circulate in the bloodstream and synthesize & secrete Ab
Antibody mediated (humoral) immune response
- Macrophages comes across an antigenic determinant
- Macrophage must find appropriate B cell with matching surface proteins to the antigenic determinant
- Helper T cells help activate and encourage reproduction of B cells by means of cytokines which give rise to plasma cells
- Ab find and antigen and mark for destruction
- Marked antigens are then easier to phagocytize
- Memory B cells created to anticipate the reappearance of certain Ag
IgM Ab
Pentamer
First to appear esp. in primary Ab response
In bloodstream on surface of B cells
IgG
Monomer
Major circulating Ab
Appears later than IgM esp. in secondary Ab response
Crosses placenta
IgA
Monomer/dimer
occurs in serum and in secretions
Secreted into mucosal surfaces, in tears, saliva, colostrum
IgE
Monomer
On surface of mast cells and plays a role in allergenic reactions
IgD
Monomer
Surface receptor on B lymphocytes
Primary Ab response
- Occurs first time Ag is encountered
- Ab begins to appear in 5 days
- First Ab is IgM then wanes
- Next Ab is IgG appears in greater amount
Secondary Ab response
- Occurs at second/subsequent Ag exposure
- Results from B memory cells
- Occurs more quickly than primary response
- Produces more Ab than primary response
- Lasts longer than primary response
Neutralizing antibodies
Viruses clump them together so they cannot enter cell
Antitoxins - alters the active sites and masks their toxicity, ^ toxins size making it easier to phagocytize
Block adhesions-binds adhesins, prevent from attaching and colonizing host
Opsonize - enhance phagosytosis; handle
Agglutinate - clump insoluble particles together making them easier to phagocytize
Precipitate - Clump soluble molecules together, making them easier to phagocytize
Activate complement - forms MAC, resulting in lysis & killing of pathogen
Natural active immunity
- Define
- Whats given to host
- Immune response
- Immune response develops naturally within a host
- Example: Getting the chicken pox
- What’s given to host: You get the virus
- Immune response is fast; after initial exposure
- Immune response is either short or long lived
Natural passive immunity
- Define
- What’s given to host?
- Immune response
- Immune response develops naturally and is provided to the host
- Example: breast milk
- What’s gien to host: Maternal Ab provided to newborn
- Immune response is fast
- Immune response lasts for 3-6 months
Artificial active immunity
- Define
- Example
- Immune response
- Immune response develops after an intentional or purposful action within the host
- Example: vaccine
- What’s actually given to host: piece of a bacterium or cead virus
- Immune response is fast
- Immune response lasts long
Artificial passive immunity
- Define
- Example
- immune response
- Immune response develops after an intentional or purposful action and is provided to host
- Snake vaccine
- immunity taken from someone else (Ab)
- Immune response is fast
- Immune response is short lived
Inactivated vaccine
- Define
- Advantage
- Concern
- Whole bacterium or virus is killed and given as an Ag
- Advantage: No danger or getting the disease from vaccine
- Concern: Releases endotoxins; short lived immunity
Attenuated Vaccine
- Define
- Advantage
- Concern
- Live organism with reduced pathogenicity is given causing a small subclinical infection
- Advantage: longer lasting immunity
- Concern: You can get sick
Subunit vaccine
- Define
- Advantage
- Concern
- Only part of the organism get infected
- Advantage: Won’t get sick;fewer side effects
- Concern: Short term immunity
Toxoid
Inactivated toxin given as Ag; has lost it’s toxic activity but retained it’s immunogenicity
EX: tetanus
Conjugated vaccine
A subunit is linked or conjugated to another molecule to increase its immunogenicity
Hapten is connected with a protein to elict greater immune response
EX: Hib vaccine
Synthetic/recombinant vaccine
A subunit or part of an organism if produced using genetic engineering
EX: hep. B vaccine & gardasil
Herd immunity
Means that it’s difficult for a disease to spread in the population if a sufficient number of individuals are immunized
90% have to be vaccinated
Adverse reactions to vaccines
Soreness at injection site, raised & red; mild fever, malaise
Due to hypersensitivity or allergy to vaccine components
wheel and flare
Hypersensitivity
an increased, exaggerated or inappropriate immune response that negatively affects the host
“Too much of a good thing”
A host is sensitized if they are hypersensitive to a particular Ag.
Allergy or allergic response
Ag is often something the host should be tolerant to
Hypersensitivity exposure
Sensitizing dose = 1st exposure; usually a large dose
Elicting dose or provocative dose = 2nd or subsequent exposure; can be quite small
Type 1 hypersensitivity
immediate-type hypersensitivity
involves IgE on the surface of mast cells and basophils and result in as immediate pharmacologic response
Ag is often an allergen
IgE binds to the surface of cells:
- Mast cells - CT cells found around respiratory & GI tracts, near blood vessels
- Basophils - granulocytes that circulate in the bloodstream
Degranulation
A rapid release of chemical substances that induce an allergic response from mast and basophil cells
Histamine dilates capillaries; immediate onset
- increase vascular permeability
- constricts smooth muscle
- increase mucus secretions
- Stimulates nerve endings > itch & pain
This reaction is called anaphylaxis
Localized anaphylaxis - local Ag exposure
Rx occurs where allergen enters body
Skin: Wheel & flare - skin Rx characterized by a swollen white center surrounded by redness & itching
Respiratory tract: bronchi constriction, weezing, cough, fluid in lungs, mucous
Digestive tract/food allergy: vomit, diahrea
Treatment: antihistamine stops the release of histamine
Asthma
Systemic anaphylaxis - Ag in bloodstream
Systemic Rx –> anaphylactic shock: blood vessels suddenly dilate and become more permeable causing a drop in blood pressure
Can be rapidly fatal (15 min)
EX: Epi pen
Treatment: desensitization-repeated injection of small amounts of denatured Ag. May prevent B cells from maturing into IgE. May induce tolerance to the Ag
Controlling type 1 hypersensitivity
Avoid contact with allergen
Antihistamine
Desensitization- repeasted injections of small amounts of denatured Ag; prevent B cells from maturing into IgE secreting plasma cells; May induce tolerance ot the Ag
Block Ab- immunize with the denatured allergen to produce serum IgG; Serum IgG blocks allergen from reaching IgE
Type 2 cytotoxic hypersensitivity
Ab usually IgG or IgM
Ag on the surface of cells
Compliment
Adverse effects appear within min-hrs
Hemolytic disease of newborn
Rh (rhesus) Ag on erythrocytes
Treatment: shot of RhoGAM - anti Rh Ab
- administered to mother at birth of first Rh+ child
- Binds up Rh Ag, preventing it from stimulating mother’s immune system
- So that Rh Ab is not produced
- Artificial Passive Immunity
Type 3 immune complex hypersensitivity
Ags - usually soluble in lrg amounts entering host
Abs - IgG or IgM
Complement
PMN’s - neutrophils
Adverse effects appear within hrs-days
Serum sickness
Type 3
Ab develops to Ags in an antiserum preperation
Next administration: Ag-Ab complexes form and damage kidneys