Immune-mediated disease Flashcards
What are the different types of immune-mediated disease
hypersensitivity (allergic disease)
autoimmune diseases
immune system neoplasia
immunodeficiency diseases/ disorders
what are the 2 categories of immune-mediated disease
primary (idiopathic)
secondary
what causes a primary immune mediated disease
caused by underlying dysfunction or imbalance in the immune system
diagnosis by exclusion of causes of secondary disease
what causes secondary immune mediated disease
infection
inflammatory disease
drugs
neoplasia
environment
define immunodeficiency
a functional problem with the immune system
what is typically seen with a primary immunodeficiency
repeated infections in young aniamls
which factors is most relevant in predisposing a dog to a primary immunodeficiency disorder
genetic
What is the most sensitive test for a diagnosis of immune mediated haemolytic anaemia
Coombs test/ direct antiglobulin test (DAT)
what 3 molecules can antibodies bind to causing IMHA/IMTP
normal self antigen
infectious agents bound to cell surface
non-biologic Ag bound to cell surface
List 6 reasons RBCs may be destroyed in IMHA
idiopathic
alloantibody present
autoantibody to RBC membrane antigen
cross-reacting antibody against infectious agent
antibody against drug adherent to RBC
drug or infection modifies RBC antigen
What is the trigger for primary IMHA
no known causative trigger
what breeds of dog tend to get primary IMHA
cocker spaniels
springers spaniels
poodles
what type of IMHA to cats tend to get
secondary- usually due to infections (e.g. mycoplasma)
what type of IMHA do dogs tend to get
primary
what is intra vascular haemolysis
direct lysis of RBCs due to antibody binding and complement activation –> releases free haemoglobin in to plasma
what do you tend to see with intravascular haemolysis
red/pink plasma
red/pink urine
what is extravascular haemolysis
antibody binding to RBCs stimulates phagocytosis by mononuclear cells in the liver and spleen
haemoglobin metabolised by liver –> haemoglobin processing produces bilirubin
how can you tell the difference between intravascular and extravascular IMHA
intravascular will have haemoglobinaemia and haemoglobinuria.
extravascular will have billirubinaemia and billirubinuria
which type of IMHA forms spherocytes
extravascular haemolysis
what do you tend to see with extra vascular haemolysis
jaundice
because the haemoglobin processing produces bilirubin
what do we seen on haematology in IMHA
PCV low
regenerative anaemia
neutrophilia
spherocytes may be present
Describe how to test for IMHA
Saline agglutination test or coombes test
describe how to perform a saline agglutination test
4 drops of saline to 1 drop EDTA blood and mix by rocking the slide
- agglutination occurs if IMHA is present
Describe the coombes test
identifies antibodies on the surface of the patient RBCs- add a load more antiserum antibodies to the sample to test if the RBCs stick
what is a spherocyte
small densely staining spherical RBCs, lack central pallor
indicator of immune-mediated haemolytic anaemia in dogs
what biochemistry results might you see with IMHA
raised liver enzymes - ALT and ALP
high billirubin and a low PCV
bilirubinaemia or haemoglobinaemia
what urinalysis results might you see with IMHA
bilirubinuria or haemoglobinuria
what infectious diseases should you screen for in IMHA patients
CATS- mycoplasma haemofelis
DOGS- babesia
Describe how IMHA is treated
treat the underlying trigger where possible- antibiotics?
Immunosuppression- glucocorticoids
what adjuvant therapy can you give with glucocorticoids in IMHA
azathioprine
Mycophenolate Mofetil
cyclosporin
leflunomide
what is primary IMTP
autoimmune disorder with production of antibodies directed against normal platelet antigens
What is secondary IMTP
antibodies target nonself antigens absorbed onto the surface of platelets or immune complexes bound to platelet surfaces
associated with: infection, drugs, neoplasia
list the clinical signs of IMTP
petechiae, echymoses, haematomas (bleeding in subcut tissues and skin)
epistaxis
gingival bleeding
melaena/ haematochezia
haematuria
retinal haemorrhage
List the lab findings seen in IMTP
low platelet count- make sure to check smear
+/- anaemia
what disease should you screen for in IMTP
ehrlichiosis
rocky mountain spotted fever
anaplasmosis
histoplasmosis
leishmaniasis
distemper
Describe how to treat IMTP
immunosuppression- prednisolone initially
transfusion
what are 3 indications to transfuse
rapidly falling PCV
clinical signs- MOST IMPORTANT (tachycardia, poor pulse, weakness, tachypnoea, collapse)
PCV <20% in dogs
PCV<15% in cats
why do we have to be very careful when treating for IMHA
it can lead to pulmonary thromboembolism - we should therefore provide a thromboprophylactic therapy as well
what is an autoimmune disease
failure of self tolerance- rare
influenced by: age, hormones, genetics, environment
