Flashcards in Pathology Deck (311)
When doing a platelet count, how many platelets per hpf is considered normal?
What is inflammation?
A complex reaction to injurious agents such as microbes and damaged (usually necrotic) cells that consists of vascular responses, migration and activation of leukocytes and systemic reactions
What are virus-neutralising antigens?
Antigens which produce a virus-neutralising antibody response
Generally structured viral proteins
Found on the outer surface of a virus
Important for reduction of infectivity
What are the mechanisms of virus-neutralising antigens?
Prevention of virus attachment
Morphological damage to virus
Inhibition of virus uncoating
Inhibition of virus replication
What are the 2 types of virus?
Live-can be attenuated, a genetic modification, or a naturally-occurring avirulent strain
Killed- unactivated products
What are the advantages and disadvantages of using live vaccines?
Advantages: humoral and cell-mediated immune responses are stimulated, more rapid protection
Disadvantages: can cause the disease, reversion to virulence
What are the advantages and disadvantages of using killed vaccines?
Advantages: humoral immunity (antibodies), adjuvants (enhance ability to protect against infection), no reversion to virulence
Disadvantages: less immunogenic (less likely to produce an immune response)
Give some reasons why a vaccine might have a lack of efficacy
Disease may be produced by a pathogen not in the vaccine
Vaccine production failure
May have been stored or administered incorrectly
Vaccines not 100%
Interference from MDA
Animal is already a carrier and is showing chronic or recrudescent disease
Give some reasons why a vaccine may have adverse reactions
Vaccine given by wrong route
Lack of attenuation or inactivation
Reaction to adjuvant
Immunocompromised animal may react to attenuated strain
Animal may already be incubating disease at time of vaccination
What is an adjuvant?
How does it work?
A substance that enhances the body's immune response to an antigen.
It works by increasing cytokine synthesis (enhanced T cell activity) and enhancing antigen presentation (enhanced B and Tc cell activity), leading to enhanced immunity
Which immunoglobulins are the main protective antibodies stimulated by vaccination?
IgG and IgA
What are the critical properties of vaccines?
Stimulation of antigen-presenting cells
Both T and B cells stimulated
Helper and effector responses to several epitopes
Vaccine antigen should persist in appropriate sites in lymphoid tissues
What is the difference between active and passive immunity?
Passive: can be natural (maternally-derived in colostrum or via placenta) or artificial (injection of antibodies from resistant to susceptible animal). No cell-mediated immunity; antibodies only. Immediate protection but only for a few weeks as antibodies wane in recipient. Risk of hypersensitivity with foreign serum.
Active: can be from natural infection or artificial immunisation. Cell-mediated immunity.
When should you not vaccinate?
If there is poor/artificial immunity
Immunity does not stop infection (ie get disease carriers)
Antibodies contribute to disease
Causes disease by infection
Vaccine antigens interfere with serodiagnosis
What are some pros and cons of living vs inactivated vaccines?
Living vaccines: few inoculating doses required, adjuvants unnecessary, relatively cheap, less chance of hypersensitivity, induction of interferon
Inactivated vaccines: stable on storage, unlikely to cause disease through residual virulence, unlikely to contain contaminating organisms, safer than live vaccines, have to be administered more often
What are the 5 kinds of virus vaccines?
Modified live virus
Recombinant product (broken down)
How do DNA vaccines work?
Cloned microbial DNA is inserted into plasmid
Cloned DNA integrates into cell genome
Cell synthesises microbial antigen
Antigen is processed and presented to T cells
Around birth, activity of which cell type is impaired and why?
Macrophage, due to increase in glucocorticoids
What is meant by tolerance to a disease (by a foetus)?
Give some examples of such diseases
Lack of immune response to specific antigens, as foetus thinks they're part of its own body
eg BHV, BVD, bluetongue
What % of transfer of immunity to offspring is via placenta and colostrum in:
Dogs and cats
Ruminants, pigs and horses
Dogs and cats: 5% placental, 95% colostral
Ruminants, pigs and horses: 100% colostral
What is the main colostral antibody?
The content of which antibody increases as colostrum production changes to milk?
How do Igs end up in colostrum?
Active transfer of Igs from blood to mammary gland under hormonal influence (oestrogen and progesterone) and local production
What is the primary immunoglobulin in non-ruminant milk?
Calves and foals need a minimum of how much colostrum in which time period?
1L within 6 hours of birth
Explain the species differences between absorption of Igs in colostrum of ruminants vs horses and pigs
Ruminants: all Igs absorbed by intestine
Horses and pigs: IgG and IgM are selectively absorbed; IgA stays in intestine (acts like an antibiotic lining)
Intestine is only permeable for a short period, declines after 6 hours, by 24 hours almost nil absorption
When are the peak levels for circulating Igs reached in the neonate?
12-24 hours after birth
What do IgG and IgA prevent?
IgG prevents septicaemia
IgA prevents enteric disease
Why do non-suckled calves make antibodies sooner than suckled calves?
Maternally-derived antibodies inhibit Ab production
How can you assess neonate Ig levels?
Zinc sulphate turbidity test (cloudier=precipitated protein of immunoglobulin)
Measure serum levels of Igs by radial immunodiffusion