Flashcards in Pathology Deck (311)
What are cytokines?
Intercellular hormones, secreted by one cell to influence another
Interleukins= from leukocytes
Control immune responses and inflammation
What do antigen-presenting cells secrete to activate Th cells and encourage their proliferation?
What are the 2 types of Th cells?
Th1: assist T cells functions eg macrophages, Tc cells. Used in intracellular infections (as antibodies can't penetrate cell)
Th2: assist B cells to make antibodies. Used in extracellular infections
What do NK cells recognise and induce?
Recognise cells without MHC Class I. Common with tumours, as tumour cells often lose MHC1 as they grow.
Which 2 breeds have a complement deficiency?
Finnish Landrace Lambs
Brittany Spaniels-congenital autosomal recessive disease
Leads to bacterial infections, glomerulonephritis in lambs
What are the 4 phases of the immune response?
1. Recognition phase: Binding of foreign Ag to specific receptors on lymphocytes
2. Activation phase: Lymphocyte proliferation, differentiation and migration
3. Effector phase: Lymphocytes act to eliminate antigen. Production of antibodies, complement, cytokine production (to enhance function of phagocytes and stimulate inflammation)
4. Memory phase: Lymphocytes with high affinity for antigen are in correct site if there is repeat infection
What is the function of Tregs? (regulatory T cells)
has surface CD4+
Switches off immune responses
Selected in thymus
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?