Chapter 22 Immunologic testing

Question 1

What is the main purpose of immunologic testing in horses?

Answer 1

To diagnose immunodeficiency following clinical signs of recurrent infections and fevers, and to identify potential inheritance of primary immune disorders.

Question 2

What type of pathogens are most commonly implicated in horse immunodeficiencies?

Answer 2

Encapsulated bacteria such as Staphylococcus aureus, Streptococcus zooepidemicus, Klebsiella spp, and Actinobacillus equuli.

Question 3

What conditions should be investigated when encapsulated bacteria are involved in horse infections?

Answer 3

B cell differentiation or function impairments, complement deficiencies, or phagocytic dysfunction.

Question 4

What infections are suggestive of faulty cellular immune mechanisms?

Answer 4

Infections with intracellular organisms like Rhodococcus equi, Pneumocystis jiroveci, Candida albicans, Aspergillus spp, and Bipolaris spp.

Question 5

What are the common clinical signs indicating possible immunodeficiency in horses?

Answer 5

Recurrent pneumonia, sinus infections, pyodermatitis, deep skin or organ abscesses, meningitis, osteomyelitis, and prolonged antibiotic therapy.

Question 6

What should immunologic testing in foals be accompanied by?

Answer 6

Age-matched and, when possible, breed-matched control samples from healthy foals.

Question 7

What is the significance of repeated tests in immunologic testing?

Answer 7

To confirm whether a condition is persistent or transient.

Question 8

What clinical history elements are essential for interpreting immunologic testing?

Answer 8

Evidence of recurrent infections, potential genetic predisposition, and familial history of immunodeficiency.

Question 9

What does a complete blood cell count and cytology help diagnose in immunodeficiency cases?

Answer 9

Infections indicated by neutrophilia, toxic changes, bands, and possible lymphopenia, anemia, or thrombocytopenia.

Question 10

What are the differential diagnoses for immunodeficiencies?

Answer 10

Leukemias and tumors (e.g., lymphosarcoma) affecting immune cell production or function.

Question 11

How is humoral function assessed?

Answer 11

By measuring serum immunoglobulin concentrations.

Question 12

What method is accurate for measuring serum IgG concentration?

Answer 12

Quantitative automated immunoturbidimetric assay.

Question 13

What is the purpose of the SNAP Foal IgG Test?

Answer 13

To provide semi-quantitative results for IgG concentrations, useful for measuring humoral protection in foals.

Question 14

What does a serum IgM concentration lower than 25 mg/dL suggest?

Answer 14

An underlying humoral dysfunction.

Question 15

What method is used to measure serum IgA concentration?

Answer 15

Enzyme-linked immunosorbent assay (ELISA), although not widely available.

Question 16

What is significant about measuring antigen-specific antibody titers in response to vaccination?

Answer 16

It evaluates in vivo immunoglobulin production.

Question 17

What does the distribution of peripheral blood B cells indicate?

Answer 17

Information about faulty humoral immunity.

Question 18

What are the markers used in peripheral blood immunophenotyping for B cells?

Answer 18

CD19, CD20, CD21, CD79a, and IgM.

Question 19

What does a decreased distribution of B cells suggest?

Answer 19

Impaired development and population expansion.

Question 20

What can humoral immunity disorders be secondary to?

Answer 20

Cellular deficiencies, particularly when CD4+ T cells cannot support B cell differentiation and survival.

Question 21

What challenges exist in assessing CD4+ and CD8+ T cell function?

Answer 21

Disorders may be intrinsic to T cells or involve upstream events of immunity.

Question 22

What can persistent lymphopenia indicate?

Answer 22

Lymphoid tissue hypoplasia or chronic disease/stress.

Question 23

What is the significance of the CD4:CD8 ratio in immunologic testing?

Answer 23

Changes in this ratio suggest immune imbalance, often secondary to infection.

Question 24

What is the role of lymphocyte proliferation assays?

Answer 24

To assess T cell function in vitro or in vivo.

Question 25

What indicates primary T cell immunodeficiencies in lymphocyte proliferation assays?

Answer 25

Inadequate proliferation in response to mitogens.

Question 26

What is phagocytosis and oxidative burst activity testing used for?

Answer 26

To assess the capacity of phagocytes to ingest and destroy pathogens.

Question 27

What method is used to measure phagocytosis and oxidative burst activity?

Answer 27

Flow cytometry using opsonized inactivated fluorescence-conjugated bacteria.

Question 28

What are complement components measured with?

Answer 28

Radial immunodiffusion (RID) or ELISA assays, and hemolytic complement assays.

Question 29

What is the significance of genetic testing in primary immunodeficiencies?

Answer 29

Provides definitive diagnosis and identifies carriers for better herd management.

Question 30

What are examples of primary immunodeficiencies identified by genetic testing?

Answer 30

Foal Immunodeficiency Syndrome (FIS) and Severe Combined Immunodeficiency Syndrome (SCID).

Question 31

What role does immunologic testing play in diagnosing neoplasms?

Answer 31

Identifies abnormal function of organs and inflammation, aiding in diagnosing tumors.

Question 32

What is the significance of immunophenotyping in neoplasm diagnosis?

Answer 32

It helps classify neoplasms based on cell lineage and stage of development.

Question 33

What is the role of DNA ploidy in diagnosing neoplasms?

Answer 33

Measures the total DNA content of cells, indicating the presence of aneuploidy.

Question 34

What are common diagnostic tests for neoplasms in horses?

Answer 34

Cytology, histopathology, immunocytochemistry, and immunohistochemistry.

Question 35

What does serum protein electrophoresis evaluate?

Answer 35

Hyperglobulinemia and monoclonal gammopathies.

Question 36

What is the role of PCR for antigen receptor rearrangement (PARR) in diagnosing lymphomas/leukemias?

Answer 36

Detects clonality and confirms lymphoid origin.

Question 37

What does immunoglobulin spectratyping assess?

Answer 37

The length of the hypervariable region CDR3 of the immunoglobulin, indicating clonality.

Question 38

What is the importance of comparing immunologic test results to confidence intervals?

Answer 38

Ensures accurate interpretation based on established normal ranges.

Question 39

What should be included in immunologic testing for suspected immunodeficiency?

Answer 39

Complete clinical history, physical examination, and blood work.

Question 40

What is the purpose of measuring cytokine production in immunologic testing?

Answer 40

To assess the activation and function of immune cells.

Question 41

What is the role of phagocytic function testing in immunologic testing?

Answer 41

Determines the ability of phagocytes to ingest and kill pathogens.

Question 42

What is the significance of complement component deficiencies?

Answer 42

Indicates impaired opsonization and increased susceptibility to infections.

Question 43

What does a positive result in immunologic testing indicate?

Answer 43

Potential immunodeficiency, requiring further investigation and management.

Question 44

What is the clinical relevance of hypo- or hypergammaglobulinemia in immunologic testing?

Answer 44

Reflects altered humoral function, potentially indicating an underlying immunodeficiency or neoplasm.

Question 45

What are the benefits of early identification of immunodeficiency in horses?

Answer 45

Guides appropriate management and treatment, improving the quality of life and survival.

Question 46

What is the purpose of using immunologic tests for allergies?

Answer 46

To identify specific allergens causing immune reactions, guiding management and treatment.