Host Defense Mechanisms and the Immune Response Flashcards
What is the order of the body’s defense mechanisms?
Invading microorganisms > physical barriers > innate immunity > specific immunity
What is included in the physical barriers (first line of defense)?
- Skin
- Coughing/sneezing
- Mucus flow
- Saliva
- Tears
- Vomiting/diarrhea
- Urine
How does the integument work to protect the body?
Through four different mechanisms:
- Desquamation
- Desiccation
- Low pH
- Resident bacteria flora
What is desquamation?
The cells on the skin continuously slough off to prevent bacteria from becoming attached to the body
What is desiccation?
Keeps the cells on the skin dry; bacteria thrive in warm, moist areas
What is low pH?
More acidic; sebaceous glands of the skin secrete sebum to keep pH low
What is resident bacteria flora?
Normal bacteria on the skin that takes up space so no abnormal/pathogenic bacteria can reside
How does the GI tract work to protect the body?
- Saliva
- Normal bacterial flora
- Low pH
- Lysozyme
How does the urinary tract work to protect the body?
- Low pH
- Urine flow
- Glycogen
Why is glycogen important for urinary tract of adult reproductive females?
Because the vagina is lined with squamous epithelium containing glycogen, therefore when cells slough off, it provides a substrate for lactobacilli
What is lactobacilli?
It produces lactic acid which keeps the pH of the vagina low
How do the mammary glands work to protect the body?
- Milk flow
- Lactenins
- Keratin plug
What is the keratin plug of the mammary glands?
It blocks T-Orifice when animal is not lactating
What is lactenins in regards to the mammary glands?
They contain compliment protein, lysozyme, and lactoferrin, which binds to bacteria so they can’t reproduce
How does the respiratory tract work to protect the body?
- Turbulence
- Particle filtration
What is turbulence in the respiratory tract?
- Turbinate bones - cause irregular airflow and warms the air
- Mucous - bacteria get caught and then either become swallowed or expelled
Why is particle size important in the respiratory tract?
It provides filtration through out
- upper respiratory - 15 um
- bronchi - 10 um
- bronchioles - 5 um
- alveoli - 1 um
Where are antibodies produced?
On mucosal surfaces
What is another work for antibodies?
Immunoglobulins
What are the four most important immunoglobulins produced in the body?
- IgA
- IgM
- IgE
- IgG
What is IgA?
- It protects body surfaces and neutralizes viruses, viral and bacterial enzymes
- Found in saliva, intestinal fluid, nasal and tracheal secretions, tears, milk, colostrum, urine and urogenital secretions
- Does not activate a compliment
What is the most important function of IgA?
Immune exclusion; it keeps things out!
What is IgM?
- Made and secreted by plasma cells in the spleen, lymph nodes, and bone marrow
- Major immunoglobulin produced in the primary immune response and with the 2nd highest concentration in blood
What is IgE?
- Backs up IgA and works through immune elimination
- Causes degranulation of mast cells and basophils by releasing histamine
- Extremely low concentrations in serum
What is the most important function of IgE?
Allergic responses to food and inhaled antigens
What is IgG?
- Found in highest concentration in the blood
- In ruminants, it is the major secretory immunoglobulin in milk and colostrum
- Smallest immunoglobulin
What is innate defense?
Immunity the animal is born with
- Complement
- Cytokines
- Lysozymes
How does complement work?
It covalently binds to specific proteins to the microbial surface to destroy invading organisims
Where is complement synthesized?
The majority is in the liver or macrophages and neutrophils store large quantities
How is complement activated?
Through binding antigen (foreign material) and antibody (immunoglobulin)
What does complement form?
MAC (membrane attack complex) at the end of the pathway to cause cell death
What are cytokines?
Chemical messengers that help to communicate through normal cells and cells of the immune system
What kinds of cells are considered cytokines?
- Interleukins
- Interferons
- Tumor Necrosis Factors (TNF)
What are interleukins?
The communicate between leukocytes and other cells in the immune system; specifically lymphocytes
What are interferons?
They are synthesized in response to viral infection, immune stimulation and to other chemical stimulus
What is the purpose of interferons?
To inhibit viral replication by stopping viral RNA and protein synthesis
What do tumor necrosis factors do?
Kills tumors by apoptosis (programmed cellular death)
Where are lysozymes found?
In all body fluids including the GI tract, but not including cerebral spinal fluid, sweat or urine with the highest concentration being in saliva, tears and neutrophils
What do lysozymes do?
Destroy bacterial peptidoglycans in the cell walls of gram positive bacteria and also act in conjunction with gram negative bacteria
What is a potent opsonin?
A lysozyme that covers an antigen to cause it to be more appetizing to phagocytic cells of the immune system
Where would you find more lysozymes?
In areas of inflammation due to their optimum pH being low (3-6) of a more acidic environment
What is inflammation?
Response of the body’s tissues to the presence of microorganisms or injury
What is inflammation triggered by?
Bacterial products or molecules produced by tissue damage
What is the body’s predominant vasoactive mediator?
Histamine except in ruminants and rodents, it’s seratonin
What is diapedesis?
The passage of blood cells through the intact walls of the capillaries, typically accompanying inflammation
What is chemotaxis?
The directed movement under the influence of a chemical gradient (aka chemical signal)
What are the cardinal signs of inflammation?
- Redness
- Heat
- Pain
- Swelling
What causes pain?
Tissue damage by an antigen which releases vasoactive factors such as histamine or serotonin
What causes redness and heat?
Vasodilation
What causes swelling?
Increased vascular permeability, as well as neutrophil margination
What was recently added as a cardinal sign of inflammation?
Loss of function
What is a neutrophil?
The major cell of the myeloid (bone marrow) system
What is the main purpose of a neutrophil?
To capture and destroy foreign particles
What is the zeta potential of a neutrophil?
Both neutrophils and bacteria suspended in blood have a degree of repulsion between adjacent, similarly charged particles, and they can be neutralized by complement and lysozymes
What are eosinophils?
They capture and and destroy foreign particles, but their main function is the destruction of parasites
Where do macrophages originate from?
Monocytes
What are the functions of macrophages?
- Phagocytosis
- Generation of nitric oxide
- Protein synthesis
- Wound healing
What does nitric oxide do?
It impedes the DNA synthesis of organisms by killing bacteria, fungi, protozoa, some worms and some tumor cells
What does protein synthesis of macrophages do?
It synthesizes and secretes lysozyme as well as proteins which act on the liver to create acute phase proteins
What proteins are produced by macrophages?
- Interleukin 1 (IL1) - regulates production of collaginance
- Interleukin 6 (IL6) - promotes antibody production
- Tumor necrosis factor - causes apoptosis
What is angiogenesis?
The creation of new blood vessels
What is the acute phase protein response?
- Microbial invasion > macrophage stimulation > cytokine production (IL1, IL6, TNF) = loss of appetite, depression, fever, neutrophilia
What does the acquired immune system protect the body from?
Foreign invaders including both extracellular and intracellular
What is an antigen?
Something foreign to the body including bacterial and viral antigens
What are some bacterial antigens?
- Flagellum - H antigen
- Pili - F antigen
- Capsule - K antigen
- Cell wall - O antigen
What are some viral antigens?
- Envelope, which is similar to cell wall
- Core - DNA or RNA depending on the virus
- Capsid - holds individual capsomeres
What is the antigenic stimulation dependent on?
- Size
- Complexity
- Stability
- Foreigness
- Epitopes
- Haptens
What are the 3 main steps of diapedesis?
Rolling -> Adherence -> Emigration
Why is size so important in antigenic stimulation?
- The bigger it is, the more antigenic it is
- Smaller antigens may be undetectable
What is the molecular weight of almost all molecules?
1000 kiladalton
Why is complexity important to antigenic stimulation?
The more complex a molecule is, the more it stands out
What are antigen presenting receptors?
Major histocomplatibility complex; including Classes I-III
How can Class I antigen presenting receptors be described?
They are viral or cancerous antigens that are found on most nucleated cells and in the highest concentration in lymphocytes (T-cells) and macrophages
How can Class II antigen presenting receptors be described?
They are external invaders (bacterial or fungus) treated by macrophages, B-cells and dendritic cells
What are dendritic cells?
Present in small quantities that are in contact with the external environment, mainly on the skin (aka Langerhans cells) and in the inner lining of the nose, lungs, stomach and intestines
How can Class III antigen presenting receptors be described?
They encode for the complement
What makes up the organs of the immune system?
The primary lymphoid organs and the secondary lymphoid organs
What are the primary lymphoid organs?
- Thymus, bursa of fabricius, peyer’s pathes, and bone marrow
- If removes, the immune system will suffer
What are the secondary lymphoid organs?
- Lymph nodes, hemolymph nodes (in cattle) and spleen
- Can be removed without issue
What are other secondary lymphoid organs?
Tonsils and digestive, respiratory, and urogenital tracts
What are T-cells?
They develop in the thymus and can be either Helper T-cells, Cytotoxic T-cells, or Memory T-cells
What do Th1 and Th2 cells do?
- Th1 cells regulate production of MHC 1 receptors
- Th2 cells stimulate B-cell proliferation
What are B-cells?
- Produced in either the bone marrow or peyer’s patch in mammals, or the bursa of fabricius in birds
- Produce antibodies, plasma cells, and memory cells
What are immunoglobulin structures composed of?
Heavy chains (Alpha, Delta, Gamma, Mu, Epsilan) and light chains (Kappa or Lamda)
Where is IgG made and how does it work?
- Made and secreted by plasma cells in the spleen, lymph nodes and bone marrow
- Works through agglutination and opsonization
How does IgM work?
Through complement activation, opsonization, virus neutralization and agglutination
What is IgD?
Primarily a B-cell receptor, but only found so far in horses, cattle, sheep, pigs, rodents and primates
In what century did the Chinese develop variolation?
12 century
What year was the innoculation against rinderpest developed?
1745 was the year the cattle plague vaccine was developed
Who and in what year improved variolation against small pox?
Edward Jenner in 1796
Who and in what year decreased virulents by inoculating birds against fowl cholera?
Louis Paster in 1879
Who and in what year first used killed organisms to prevent infections?
Daniel Salmon and Theobald Smith in 1879
Who and in what year used a toxoid instead of an organism to vaccinate horses against tetanus?
Emil von Behring and Shibasaburo Kitasato in 1890
What are the different phases included in the immune response?
- Lag Phase
- Log Phase
- Plateau
- Decline
What does the lag phase of the immune response include?
It is the initial phase of the antibody response where antibodies are not detectable; the time from inoculation of an organism to the time the body mounts a measurable response
What does the log phase of the immune response involve?
Exponential increase in antibody production
What does the plateau phase of the immune response involve?
The production of antibodies is equal to the catabolic breakdown of antibodies
What is included in the decline phase of the immune response?
When the catabolism exceeds the synthesis and antibodies are all being used or are dying
What happens during the primary immune response?
The level of antibodies produced in small (primarily IgM), as well as the protection against an infectious agent
Is the secondary immune response lag phase shorter or longer than the primary phase?
Shorter
Which immune response produces more antibodies?
The secondary immune response
Is the secondary immune response log phase faster or shorter?
Faster
Is the antibody production during the secondary immune response higher or lower than the primary immune response?
Much higher
What are the primary antibodies produced during the secondary immune response?
IgG
What are the two different types of immunization?
Passive and active immunity
What is passive immunity?
The transfer of antibodies that have already been produced from another animal
What are the two types of passive immunity?
- Natural (colostrum) or artificial (vaccines)
- Immediate but temporary
What is active immunization?
When an antigen stimulates an immune response; protection is not conferred immediately but it is long lasting
Is active immunization capable of restimulation?
Yes it is capable of secondary response
What are the different types of biologicals?
- Antiserum
- Antitoxin
- Toxoid
- Bacterin
What is antiserum?
Serum that contains specific antibodies
What is antitoxin?
Antiserum directed against a toxin
What is a toxoid?
A non-toxic derivative of toxins used as antigens
What is a bacterin?
A preparation of killed bacteria used for immunization
What kind of biologicals are part of passive immunization?
Antiserum and antitoxin
What kind of biologicals are part of active immunization?
Toxoid and bacterin
What three things are involved in the manufacturing of biologicals?
- Attenuation
- Inactivation
- Adjuvant
What is attenuation?
The reduction of virulence of an infectious agent aka a modified live vaccine
What is inactivation?
Treatment of an infectious agent so that it can no longer replicate aka a killed vaccine
What is adjuvant?
- Any substance given with an antigen that enhances the immune response to that antigen
- A chemical irritant to activate the immune system to make it response faster
What are some pros to using a modified live vaccine?
- There are few inoculating doses required with less chance of hypersensitivity
- They are relatively cheap and adjuvants are unnecessary
- There is residual virulence with the induction of interferons
What is a con of a modified live vaccine?
They still have the ability to cause disease if the virus reverts back to its “wild type”
What are some pros of using a killed vaccine?
- They are stable on storage and unlikely to cause disease
- Unlikely to contain a contaminating organism
What are some other examples of modified live vaccines?
- Purified Subunits
- Recombinant Product
- DNA Vaccine
What is a purified subunit modified live vaccine?
It uses only part of the disease causing virus
What is a recombinant product modified live vaccine?
It involves inserting the DNA and encoding an antigen that stimulates an immune response into bacterial or mammalian cells, expressing the antigen in those cells and then purifying it from them
What is a DNA modified live vaccine?
It protects against disease by injection with genetically engineered DNA so cells directly produce an antigen, producing a protective immunological response
What is the licensing of vaccines cascading order?
- United States Department of Agriculture
- Animal and Plant Health Inspection Service
- Veterinary Services
- Center for Veterinary Biologicals
How many categories are in the USDA Classification of Genetically Engineered Biologicals?
I-III
What is category I of the classification of biologicals?
Vaccines that contain purified antigens derived from recombinant organisms (ex: FeLV and Lyme)
What is category II of the classification of biologicals?
Vaccines containing live organisms that contain gene deletions or “knock out genes” (ex: Pseudorabies)
What is category III of the classification of biologicals?
Contains live expression vectors containing heterologous genes for immunizing antigens (ex: Oral Rabies Bait)
What is the vaccine assessment?
What must be established by the immune system so that it can be protected against the disease in question, and that the risk of vaccination do not exceed those associated with the chance of contacting the disease itself
What is the preventable fraction?
Should be at least 80%
What is the only exception to the preventable fraction?
Rabies because it needs to be at least 90%
What is herd immunity?
- Immunity conferred on a population as a result of the presence of immune individuals within a population
- It reduces the probability of a susceptible animal meeting an infected one so that the spread of disease is slowed or terminated
