Immunology & Serology

A kitten tests positive for high IgM against panleukopenia but low IgG

Current or recent infection

A dog presents with sneezing and elevated IgE

Hypersensitivity (allergic) reaction

A senior cat has high IgG for FIV but low IgM

Chronic or past infection

What does IgA primarily protect against?

Mucosal pathogens

Which immunoglobulin provides long-term immunity?

IgG

Which immunoglobulin is first produced during infection?

IgM

Which immunoglobulin is involved in allergic responses and parasites?

IgE

Which immunoglobulin activates B cells but is poorly understood?

IgD

Which immunoglobulin is found in colostrum and protects mucosa?

IgA

Which antibody would be tested to detect early-stage infection?

IgM

What does the immune system consist of?

Cells (lymphocytes, monocytes, macrophages), tissues (bone marrow, GIT submucosa), and organs (skin, spleen, thymus, liver, lymph nodes).

What are the two divisions of the immune system?

Innate (non-specific) immunity and acquired (adaptive/specific) immunity.

What are the components of innate immunity?

Skin, mucous membranes, neutrophils, monocytes, macrophages, colostrum, and normal flora.

What is humoral immunity mediated by?

B-lymphocytes that produce antibodies and memory cells.

What are the five types of immunoglobulins and their functions?

IgG: Most abundant, crosses placenta; IgM: First produced, current infection; IgA: Mucosal protection; IgD: Activates B cells; IgE: Allergic reactions

What is cellular immunity mediated by?

T-lymphocytes that bind antigens; important in viruses, fungi, cancer cells, and transplants.

What is serology?

The study of serum to detect antibodies or antigens.

What is the purpose of monoclonal antibodies?

Lab-made antibodies specific to one antigen, used in diagnostic tests like ELISA and SNAP.

How does ELISA work and what does it detect?

Uses enzyme-linked detection to measure antigen or antibody via color change.

When is CELISA used and how does it work?

For low-concentration antigens; patient antigen competes with enzyme-linked antigen.

What does agglutination detect?

Antigen-antibody clumping; used in IMHA, Cryptococcus, and Parvo diagnosis.

How do you differentiate rouleaux from true agglutination?

Add saline — rouleaux disperses, true agglutination does not.

What does the Coombs test detect?

Antibodies coating RBCs — used to diagnose IMHA.

How does a RIM (Rapid Immunomigration) test work?

Uses colloidal gold and antibody binding to create a visible line.

What is immunodiffusion used for?

Detects large antigen-antibody precipitates; used in EIA (Coggins), Johne’s disease.

What does intradermal testing assess?

IgE-mediated allergy response or delayed cell-mediated response (e.g., TB test).

What are the important blood types in dogs, cats, and horses?

Dogs: DEA 1 (universal donor = DEA 1-); Cats: A, B, AB (naturally occurring antibodies); Horses: A, Q (NI common)

What is the purpose of cross-matching blood?

To check for serological compatibility between donor and recipient.

What is neonatal isoerythrolysis in cats?

Type B queen nurses type A kittens; anti-A antibodies in colostrum cause hemolysis.

What is neonatal isoerythrolysis in horses?

Fetal blood leaks into mare → antibodies form → foal ingests them → RBC destruction.