Immunodeficiency Overview
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Questions and Answers

What is a common clinical symptom associated with Chédiak-Higashi Syndrome?

  • Hypersensitivity to sunlight
  • Loss of skin color and dilution of hair pigmentation (correct)
  • Increased joint mobility
  • Chronic fatigue syndrome

What type of genetic mutation is involved in Chédiak-Higashi Syndrome?

  • Deletion mutation
  • Frameshift mutation
  • Nonsense mutation
  • Missense mutation (correct)

Which of the following is a consequence of the immunological defects in Chédiak-Higashi Syndrome?

  • Increased chemotactic activity of neutrophils
  • Reduced intracellular cytotoxicity (correct)
  • Decreased susceptibility to viral infections
  • Enhanced cytokine production

Which cells are primarily affected in Chédiak-Higashi Syndrome leading to large secretory lysosomes?

<p>Neutrophils, monocytes, eosinophils, and melanocytes (A)</p> Signup and view all the answers

What is a potential complication arising from the rapturing of granules in cytotoxic cells of individuals with Chédiak-Higashi Syndrome?

<p>Tissue damage leading to lesions (A)</p> Signup and view all the answers

What is an effect of Chédiak-Higashi Syndrome on susceptibility to infections?

<p>Reduced activity of neutrophils (B)</p> Signup and view all the answers

What condition might neonates with Chédiak-Higashi Syndrome develop?

<p>Septicemia (D)</p> Signup and view all the answers

What is a common symptom associated with cyclic neutropenia?

<p>Recurrent respiratory tract infections (A)</p> Signup and view all the answers

Which diagnostic criterion is essential for confirming SCID in horses?

<p>Absence of IgM in serum before suckling (D)</p> Signup and view all the answers

What immunological defect is central to Severe Combined Immunodeficiency Disease (SCID)?

<p>Defect in DNA-PKcs (C)</p> Signup and view all the answers

Which of the following disorders involves a defect in the gamma chain of the IL-2 receptor?

<p>X-linked Severe Combined Immunodeficiency (X-SCID) (A)</p> Signup and view all the answers

Which is a significant indicator of Chédiak-Higashi Syndrome in affected animals?

<p>Presence of giant lysosomal granules (D)</p> Signup and view all the answers

What is a common indicator of primary immunodeficiency in young animals?

<p>Chronic or recurrent infections (B)</p> Signup and view all the answers

Which diagnostic procedure can help assess humoral immunity?

<p>Determination of Ab response to vaccine antigens (B)</p> Signup and view all the answers

What is a key feature of the Chédiak-Higashi Syndrome (CHS)?

<p>Mutation occurs in the lyst (CHS1) gene (A)</p> Signup and view all the answers

Persistent leukopenia or hypogammaglobulinemia is indicative of what?

<p>An underlying immunodeficiency (B)</p> Signup and view all the answers

Which of the following is typically assessed to determine the function of neutrophils?

<p>Mitogen injection response (A)</p> Signup and view all the answers

What is a critical step in diagnosing primary immunodeficiency?

<p>Localizing the immunological defect (D)</p> Signup and view all the answers

What type of immune dysfunction might Chédiak-Higashi Syndrome involve?

<p>Failure of phagocytosis and cell-mediated responses (B)</p> Signup and view all the answers

Which of the following conditions is linked to defects in innate immunity?

<p>Chédiak-Higashi Syndrome (A)</p> Signup and view all the answers

What laboratory test can assist in determining a young animal's immune responses?

<p>Assessment of CD4+:CD8+ lymphocyte ratio (D)</p> Signup and view all the answers

What is an important aspect of diagnosing an immunodeficiency linked to chronic infections?

<p>Determining the presence of atypical microorganisms (C)</p> Signup and view all the answers

Flashcards

CHS Gene Mutation

A mutation in a gene causing a protein change that disrupts lysosomal membrane trafficking.

Lysosomal Membrane Trafficking

The process of transporting materials within lysosomes, small compartments in cells that break down waste.

CHS Symptoms (Eye)

CHS (Chédiak-Higashi Syndrome) can cause cataracts and photophobia (eyes sensitive to light).

CHS Symptoms (Skin)

CHS can cause loss of skin color and diluted hair.

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CHS Symptoms (Immune System)

CHS weakens the immune system, leading to a higher risk of infections, especially respiratory infections.

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CHS Symptoms (Blood Clotting)

CHS causes issues with blood clotting and easy bruising, also referred as bleeding abnormally.

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Granule Fusion & Rupture

Granules (packages of cells' waste) may fuse, rupture, and potentially lead to tissue damage. This can also affect the eye.

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Cyclic neutropenia in dogs

A hereditary disorder causing periodic drops in neutrophil blood cell count, leading to infections due to a weakened immune response.

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Severe Combined Immunodeficiency (SCID) in horses

An inherited genetic defect hindering the development of T and B lymphocytes, causing a severe deficiency in the immune system.

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Molecular basis of SCID in horses

A defect in the DNA-PKcs enzyme, disrupting DNA recombination processes necessary for T-cell/B-cell receptor development.

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X-linked SCID in dogs

An inherited immune deficiency, exclusively affecting males, caused by mutations affecting crucial immune-related molecules like IL-2 receptor γ chain.

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Diagnosis of SCID in horses

Confirming SCID requires low lymphocyte counts, absence of IgM before feeding, and specific characteristic histological findings in lymphatic tissue.

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Chronic Infections in Young Animals

Recurring infections in young animals, often unresponsive to standard treatments like antibiotics, and potentially affecting multiple body sites.

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Immunodeficiency Diagnosis

Locating the specific immune system component causing the problem, using various tests for cell-mediated and humoral immunity.

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Hematology Profile

Blood test analyzing various components like red blood cells, white blood cells, and platelets.

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Immune System Testing

Evaluating the immune response by checking antibody production to vaccine and functional neutrophil and macrophage activity.

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Immunophenotyping

Analyzing the surface markers of immune cells (like lymphocytes) to identify their type and function.

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CD4+:CD8+ Ratio

A ratio measuring the proportion of CD4+ to CD8+ lymphocytes, often indicative of immune health.

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Innate Immunity Defects

Problems within the body's initial immune defenses, affecting things like phagocytosis, complement system, and NK cell function.

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Chédiak-Higashi Syndrome

Genetic disorder causing abnormal immune cells (phagocytes) and a range of issues in different species.

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Genetic Testing

Use of genetic tools to diagnose animal diseases like SCID, related to the immune system.

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Severe Combined Immune-deficiency (SCID)

Genetic disorder causing a severe deficiency in both the cellular and humoral immune systems.

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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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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.

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