Chapter 22 Immunologic testing Flashcards
What is the main purpose of immunologic testing in horses?
To diagnose immunodeficiency following clinical signs of recurrent infections and fevers, and to identify potential inheritance of primary immune disorders.
What type of pathogens are most commonly implicated in horse immunodeficiencies?
Encapsulated bacteria such as Staphylococcus aureus, Streptococcus zooepidemicus, Klebsiella spp, and Actinobacillus equuli.
What conditions should be investigated when encapsulated bacteria are involved in horse infections?
B cell differentiation or function impairments, complement deficiencies, or phagocytic dysfunction.
What infections are suggestive of faulty cellular immune mechanisms?
Infections with intracellular organisms like Rhodococcus equi, Pneumocystis jiroveci, Candida albicans, Aspergillus spp, and Bipolaris spp.
What are the common clinical signs indicating possible immunodeficiency in horses?
Recurrent pneumonia, sinus infections, pyodermatitis, deep skin or organ abscesses, meningitis, osteomyelitis, and prolonged antibiotic therapy.
What should immunologic testing in foals be accompanied by?
Age-matched and, when possible, breed-matched control samples from healthy foals.
What is the significance of repeated tests in immunologic testing?
To confirm whether a condition is persistent or transient.
What clinical history elements are essential for interpreting immunologic testing?
Evidence of recurrent infections, potential genetic predisposition, and familial history of immunodeficiency.
What does a complete blood cell count and cytology help diagnose in immunodeficiency cases?
Infections indicated by neutrophilia, toxic changes, bands, and possible lymphopenia, anemia, or thrombocytopenia.
What are the differential diagnoses for immunodeficiencies?
Leukemias and tumors (e.g., lymphosarcoma) affecting immune cell production or function.
How is humoral function assessed?
By measuring serum immunoglobulin concentrations.
What method is accurate for measuring serum IgG concentration?
Quantitative automated immunoturbidimetric assay.
What is the purpose of the SNAP Foal IgG Test?
To provide semi-quantitative results for IgG concentrations, useful for measuring humoral protection in foals.
What does a serum IgM concentration lower than 25 mg/dL suggest?
An underlying humoral dysfunction.
What method is used to measure serum IgA concentration?
Enzyme-linked immunosorbent assay (ELISA), although not widely available.
What is significant about measuring antigen-specific antibody titers in response to vaccination?
It evaluates in vivo immunoglobulin production.
What does the distribution of peripheral blood B cells indicate?
Information about faulty humoral immunity.
What are the markers used in peripheral blood immunophenotyping for B cells?
CD19, CD20, CD21, CD79a, and IgM.
What does a decreased distribution of B cells suggest?
Impaired development and population expansion.
What can humoral immunity disorders be secondary to?
Cellular deficiencies, particularly when CD4+ T cells cannot support B cell differentiation and survival.
What challenges exist in assessing CD4+ and CD8+ T cell function?
Disorders may be intrinsic to T cells or involve upstream events of immunity.
What can persistent lymphopenia indicate?
Lymphoid tissue hypoplasia or chronic disease/stress.
What is the significance of the CD4:CD8 ratio in immunologic testing?
Changes in this ratio suggest immune imbalance, often secondary to infection.
What is the role of lymphocyte proliferation assays?
To assess T cell function in vitro or in vivo.
What indicates primary T cell immunodeficiencies in lymphocyte proliferation assays?
Inadequate proliferation in response to mitogens.
What is phagocytosis and oxidative burst activity testing used for?
To assess the capacity of phagocytes to ingest and destroy pathogens.
What method is used to measure phagocytosis and oxidative burst activity?
Flow cytometry using opsonized inactivated fluorescence-conjugated bacteria.
What are complement components measured with?
Radial immunodiffusion (RID) or ELISA assays, and hemolytic complement assays.
What is the significance of genetic testing in primary immunodeficiencies?
Provides definitive diagnosis and identifies carriers for better herd management.
What are examples of primary immunodeficiencies identified by genetic testing?
Foal Immunodeficiency Syndrome (FIS) and Severe Combined Immunodeficiency Syndrome (SCID).
What role does immunologic testing play in diagnosing neoplasms?
Identifies abnormal function of organs and inflammation, aiding in diagnosing tumors.
What is the significance of immunophenotyping in neoplasm diagnosis?
It helps classify neoplasms based on cell lineage and stage of development.
What is the role of DNA ploidy in diagnosing neoplasms?
Measures the total DNA content of cells, indicating the presence of aneuploidy.
What are common diagnostic tests for neoplasms in horses?
Cytology, histopathology, immunocytochemistry, and immunohistochemistry.
What does serum protein electrophoresis evaluate?
Hyperglobulinemia and monoclonal gammopathies.
What is the role of PCR for antigen receptor rearrangement (PARR) in diagnosing lymphomas/leukemias?
Detects clonality and confirms lymphoid origin.
What does immunoglobulin spectratyping assess?
The length of the hypervariable region CDR3 of the immunoglobulin, indicating clonality.
What is the importance of comparing immunologic test results to confidence intervals?
Ensures accurate interpretation based on established normal ranges.
What should be included in immunologic testing for suspected immunodeficiency?
Complete clinical history, physical examination, and blood work.
What is the purpose of measuring cytokine production in immunologic testing?
To assess the activation and function of immune cells.
What is the role of phagocytic function testing in immunologic testing?
Determines the ability of phagocytes to ingest and kill pathogens.
What is the significance of complement component deficiencies?
Indicates impaired opsonization and increased susceptibility to infections.
What does a positive result in immunologic testing indicate?
Potential immunodeficiency, requiring further investigation and management.
What is the clinical relevance of hypo- or hypergammaglobulinemia in immunologic testing?
Reflects altered humoral function, potentially indicating an underlying immunodeficiency or neoplasm.
What are the benefits of early identification of immunodeficiency in horses?
Guides appropriate management and treatment, improving the quality of life and survival.
What is the purpose of using immunologic tests for allergies?
To identify specific allergens causing immune reactions, guiding management and treatment.
