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Questions and Answers
What is a common clinical symptom associated with Chédiak-Higashi Syndrome?
What is a common clinical symptom associated with Chédiak-Higashi Syndrome?
What type of genetic mutation is involved in Chédiak-Higashi Syndrome?
What type of genetic mutation is involved in Chédiak-Higashi Syndrome?
Which of the following is a consequence of the immunological defects in Chédiak-Higashi Syndrome?
Which of the following is a consequence of the immunological defects in Chédiak-Higashi Syndrome?
Which cells are primarily affected in Chédiak-Higashi Syndrome leading to large secretory lysosomes?
Which cells are primarily affected in Chédiak-Higashi Syndrome leading to large secretory lysosomes?
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What is a potential complication arising from the rapturing of granules in cytotoxic cells of individuals with Chédiak-Higashi Syndrome?
What is a potential complication arising from the rapturing of granules in cytotoxic cells of individuals with Chédiak-Higashi Syndrome?
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What is an effect of Chédiak-Higashi Syndrome on susceptibility to infections?
What is an effect of Chédiak-Higashi Syndrome on susceptibility to infections?
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What condition might neonates with Chédiak-Higashi Syndrome develop?
What condition might neonates with Chédiak-Higashi Syndrome develop?
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What is a common symptom associated with cyclic neutropenia?
What is a common symptom associated with cyclic neutropenia?
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Which diagnostic criterion is essential for confirming SCID in horses?
Which diagnostic criterion is essential for confirming SCID in horses?
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What immunological defect is central to Severe Combined Immunodeficiency Disease (SCID)?
What immunological defect is central to Severe Combined Immunodeficiency Disease (SCID)?
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Which of the following disorders involves a defect in the gamma chain of the IL-2 receptor?
Which of the following disorders involves a defect in the gamma chain of the IL-2 receptor?
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Which is a significant indicator of Chédiak-Higashi Syndrome in affected animals?
Which is a significant indicator of Chédiak-Higashi Syndrome in affected animals?
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What is a common indicator of primary immunodeficiency in young animals?
What is a common indicator of primary immunodeficiency in young animals?
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Which diagnostic procedure can help assess humoral immunity?
Which diagnostic procedure can help assess humoral immunity?
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What is a key feature of the Chédiak-Higashi Syndrome (CHS)?
What is a key feature of the Chédiak-Higashi Syndrome (CHS)?
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Persistent leukopenia or hypogammaglobulinemia is indicative of what?
Persistent leukopenia or hypogammaglobulinemia is indicative of what?
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Which of the following is typically assessed to determine the function of neutrophils?
Which of the following is typically assessed to determine the function of neutrophils?
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What is a critical step in diagnosing primary immunodeficiency?
What is a critical step in diagnosing primary immunodeficiency?
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What type of immune dysfunction might Chédiak-Higashi Syndrome involve?
What type of immune dysfunction might Chédiak-Higashi Syndrome involve?
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Which of the following conditions is linked to defects in innate immunity?
Which of the following conditions is linked to defects in innate immunity?
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What laboratory test can assist in determining a young animal's immune responses?
What laboratory test can assist in determining a young animal's immune responses?
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What is an important aspect of diagnosing an immunodeficiency linked to chronic infections?
What is an important aspect of diagnosing an immunodeficiency linked to chronic infections?
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Study Notes
Immunodeficiency
- Immunodeficiency is a failure in humoral or cell-mediated limbs of the immune response.
- Primary immunodeficiency (congenital) stems from genetic defects in one or more immune system components.
- Secondary immunodeficiency (acquired) arises from loss of function in antibodies or lymphocytes.
- The term also encompasses defective leukocytes and complement system.
Objectives
- Define immunodeficiency.
- Define primary and secondary immunodeficiencies.
- Describe the possibilities of diagnosing immunodeficiency.
- Describe the nature and possible causes of congenital immunodeficiency.
- Describe the nature and possible causes of acquired immunodeficiency.
What is Immunodeficiency?
- Immunodeficiency is a failure in humoral or cell-mediated aspects of the immune response.
- Primary immunodeficiency is due to intrinsic defects in T and/or B lymphocytes.
- Secondary immunodeficiency arises from loss of function in antibodies and/or lymphocytes.
- The term can also refer to defective leukocytes or the complement system.
Primary Immunodeficiency
- A result of one or more genetic defects in immune system components.
Stages of Immune Cell Development
- Failure of differentiation of the pluripotent stem cell.
- Failure of differentiation of the lymphoid/myeloid lineage.
- Failure of T cell development.
- Failure of B cell development.
- Blockade of B cell differentiation into plasma cells.
- Failure of plasma cells to produce selected classes of immunoglobulin (Ig).
- Failure to produce functional neutrophils and macrophages.
- Failure to produce one or more complement components.
When to Suspect Primary Immunodeficiency
- Chronic or recurrent infections in young animals.
- Failure to respond to antibiotics or chemotherapy.
- Multiple-site infections in young animals or littermates.
- Infections with atypical microorganisms (e.g., saprophytes or commensals).
- Lack of response to vaccine antigens.
- Persistent leukocytosis or hypergammaglobulinemia.
- Persistent leukopenia or hypogammaglobulinemia.
- Allergy or concurrent autoimmune disease.
Diagnosis of Primary Immunodeficiency
- The goal is to pinpoint the immunological defect(s) in one or more immune system components.
- Ideally, a full panel of tests targeting cell-mediated and humoral immunity is used.
Diagnostic Procedures
- Hematology profile.
- Bone marrow and lymph node biopsy.
- Determination of complement component concentration in serum.
- Screening for infectious diseases using serological and molecular techniques.
- Full necropsy of dead littermates.
- Determination of antibody response to vaccine antigens.
- Immunophenotyping of lymphocytes (e.g., CD4+:CD8+ ratio).
- Functional testing for neutrophils and macrophages.
- Assessment of delayed-type hypersensitivity using mitogens (e.g., PHA).
- Confirm atypical results at least twice.
- Genetic testing is becoming available for certain conditions.
Immunodeficiencies Associated with Innate Immunity
- Defects at various stages of phagocytosis.
- Deficiencies in function of the complement system.
- Dysfunction of NK cells.
Chediak-Higashi Syndrome (CHS)
- Found in various species (mink, cats, humans, etc.).
- Cause: Mutation in the lyst (CHS1) gene, affecting lysosomal membrane trafficking.
- Defective proteins lead to large secretory lysosomes and granules.
- Clinical Presentation: Loss of skin color, hair dilution, eye abnormalities (cataracts, photophobia), increased susceptibility to infections (especially respiratory tract), bleeding tendency, and susceptibility to tumors.
- Diagnosis: Stained blood smears reveal enlarged granules in neutrophils, molecular testing (humans).
- Treatment: Symptomatic.
Canine Leukocyte Adhesion Deficiency (CLAD)
- Cause: Lack of integrin CD11b/CD18 (Mac-1).
- Neutrophils unable to react to chemotactic factors and adhere to blood vessel endothelium.
- Clinical presentation: Animals die of severe infections, impaired pus formation, delayed wound healing; leukocytosis with neutrophilia and eosinophilia.
- Lack of leukocyte migration to inflammation sites.
- Recurrent infections despite high neutrophil count.
- Abnormal blood clotting.
Bovine Leukocyte Adhesion Deficiency (BLAD)
- Found in Holstein calves.
- Clinical presentation similar to CLAD.
- Affected calves die between 2 and 7 months of age.
Common Variable Immunodeficiency (CVID)
- B lymphocytes fail to produce adequate levels of immunoglobulin.
- Possible causes: Lack of proper stimulation of B cells by helper T cells.
- Appears in older horses (typically over 3 years of age).
- Leads to frequent infections (e.g., bacterial meningitis).
- Normal or low levels of IgM and IgG, while IgG levels may be normal.
- Low T-lymphocyte numbers.
- Few B-lymphocytes in lymphoid tissue.
Severe Combined Immunodeficiency (SCID)
- Primarily in Arabian horses.
- Severe deficiency in T and B lymphocytes.
- Foals appear healthy at birth, but develop health issues within 2 months of age.
- Affected foals receive adequate antibodies from colostrum and milk for the first couple of months post-birth, and often die of bacterial, viral, and fungal infections.
- Histological signs: absence of germinal centers and lymphoid follicles.
- Diagnostic criteria: include few circulating lymphocytes, low IgM, and typical histological changes in lymph and immune tissues.
Secondary Immunodeficiencies
- Damage to the normal immune system due to: infectious agents (e.g., viruses), toxins, stress, malnutrition, old age (immunosenescence).
Virus Infection-Induced Immunosuppression
- Viruses may damage primary or secondary lymphatic organs.
- May lead to lymphopenia.
- May reduce lymphocyte reactivity to stimulation.
- May lead to hypogammaglobulinemia.
Viruses that Cause Damage to Lymphatic Tissue
- Includes a table of various viruses.
Viruses that Highly Stimulate Lymphoid Tissue Activity and Neoplasia
- Includes a table of specific viruses.
Canine Distemper Virus
- Initially attacks lymphoid tissue in tonsils, bronchial lymph nodes, and blood.
- Damages cells in spleen, MALT, and thymus.
- Causes lymphopenia, which leads to immune suppression.
- Reduces production IL-1 and IL-12.
- Vulnerability to infections with Pneumocystis carinii.
Feline Leukemia Virus (FeLV)
- FeLV infects lymphoid tissue.
- Attacks and reduces CD4+ T cells.
- Wasting syndrome develops due to ongoing infections and atrophy of the thymus.
- Secondary infections could lead to atrophy or hyperplasia of lymphoid tissue, which leads to immunosuppression.
Feline Immunodeficiency Virus (FIV)
- This virus infects cats.
- It replicates in lymphocytes, particularly CD4+ T cells, B cells, and macrophages.
- FIV attaches to CD134 and CD184 (CXCR4).
- Infection reduces CD4+ cell numbers.
- Leads the reduction of IL-2 production.
- It activates CD4+/CD25+ Treg cells, thereby deepens immuno-suppression.
- Increases production of IL-10 resulting in immunosuppression.
Immunosenescence
- Gradual decline in immune function with age.
- Affects various immune cells (e.g., T cells, NK cells, macrophages, B cells, dendritic cells).
- Diminished antigen presentation, cytokine production, and cytotoxicity.
Selective Immunoglobulin Isotype Deficiencies
- Selective involvement and deficiency in one or a few immunoglobulin (Ig) classes.
- Most commonly associated with selective IgA deficiency.
- Potential causes: Block in B-cell differentiation to IgA/IgG-producing cells, homozygous deletions of constant region genes.
Selective Immunoglobulin Deficiencies in Dogs
- Various types affecting specific immunoglobulin classes (e.g., IgG, IgM).
- Clinical signs can include recurrent infections.
- Cause(s) unclear or not described precisely.
Common Variable Immunodeficiency (CVID) in other species
- B lymphocytes do not produce adequate levels of Ig.
- Appears in older animals over 3 years of age.
- Frequent infections.
- Possible causes include lack of appropriate stimulation from helper T cells or genetic defects.
- Possible signs: Low levels or trace levels of IgM, IgG while IgG3 normal.
- Possibly have deficient co-stimulatory molecule ICOS (in humans).
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Description
Explore the concept of immunodeficiency, including its types, primary and secondary forms. This quiz covers the definitions, causes, and implications of congenital and acquired immunodeficiency, as well as diagnostic possibilities.
