Equine Immunology and Hematology I Flashcards by Emma Mortensen

What are components of Innate immunity?

Nonspecific
Acute phase proteins
-Fibrinogen
Proinflammatory cytokines
-IL-1, IL-6, TNFalpha
Complement system
Lipid mediators
-Prostaglandins, leukotrienes
Granulocytes, monocytes

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Components of Adaptive immunity

Specificity and memory
Cellular and humoral (Ab mediated)
B cell lymphocytes
- Memory cells
- Immunoglobulins
T-cell lymphocytes
-CD8, CD4
-MHC

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Neutrophilia causes in the horse

Chronic/established infection
Abscess
Neoplasia, glucocorticoids

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Neutropenia causes in the horse

Acute, severe infection (GI)
Septicemia, endotoxemia
- L shift and toxic changes
Endotoxemia is rapid redistribution of N0 to marginal and tissue pools

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Lymphopenia causes

Acute viral, rickettsial, or severe bacterial infection

Endotoxemia

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Eosinophilia causes

Parasitic
Hypersensitivity
Neoplasia

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Basophilia causes

Hypersensitivity

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Immunodeficiencies

Primary (rare): genetic
Secondary: altered responses of normal immune system
- Disease (PPD)
- Age
- Pregnancy
- Drugs
- Stressors
- Neoplasia
- Malnutrition, nutrient deficiencies

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Clinical features of immunodeficiency

Onset at young age
Repeat infections, poorly responsive to treatment
Increased susceptibility to organisms of low pathogenicity
Illness or poor immunologic response to vaccination
Persistent abnormalities in leukocytes

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Dx of immunodeficiency

Ab mediated immunity: quantitative tests for Ig levels, functional test of response to vax
Cellular immunity: Quantitative CBC, lymphocyte phenotyping, functional test response to vax
Granulocytes, monocytes, M0: quantitative only
Bone marrow: evaluate progenitor cell populations

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SCID

Lethal, autosomal recessive condition primarily seen in Arabian foals
- Chromosome 9 mutation
- 8-25% Arabians in US are carriers
T and B cell function absent
- Absence of cell mediated and Ab mediated immunity

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Other rare immunodeficiencies

Common variable immunodeficiency
- Late onset (6-14yr) no breed or gender disposition
- Recurrent bacterial infections
IgM dificiency
Agammaglobulinemia
Transient hypogammaglobulinemia
Fell pony syndrome

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Lymphoproliferative disorders

Lymphoma
Leukemia
Myeloma

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Equine lymphoma basics

Most common neoplasia of the horse

Mean diagnostics 5-10y

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CS of equine lymphona

Lymphadenopathy
Lethargy, weight loss, fever
Others dependent
Peripheral lymphadenopathy rare
Hematologic abnormalities are variable
- Anemia, lymphopenia
- Lymphocyte morphology abnormal
- Inflammatory leukogram, hyperglobulinemia
Paraneoplastic syndromes
- Hypercalcemia
- Immune mediated Hemolytic anemia or thrombocytopenia
Occasional suspect association with EHV 5

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Equine lymphoma classification

Morphologic: small cell, large cell, mixed
Cell lineage: immunohistochemical evaluation, T cell rich, large b cell most common
Anatomic distribution: multicentric, generalized, alimentary/intestinal, thoracic, cutaneous

Multicentric lymphoma

Multiple lymph nodes

No extra nodal involvement

Generalized lymphoma

Metastasis to extra-nodal tissues
Nonlymphoid tissue involved
Spleen most common organ
Very poor prognosis
Severe clinical signs
Leukemia possible

Intestinal lymphoma

CS: malabsorption, PLE, weight loss, edema, abdominal effusion, colic, diarrhea
Neoplastic lesions: diffuse, segmental thickening, focal masses, scattered ulcerative lesions
Dx: US, biopsy, Abd fluid analysis

MOST common neoplasia of GIT
Lymphadenopathy not typical

Thoracic lymphoma

Most common thoracic neoplasia; Mediastinal, thymic, or pulmonary T cell predominates
CS nonspecific: Nasal discharge, adventitial lung sounds, pleural effusion*, ventral thoracic and limb edema, lymphadenopathy

Cutaneous lymphoma

Skin associated lymphoid tissue
Distribution variable; single to multiple firm, SQ, nonpainful masses
Predominantly T cell rich large B cell
Often aggressive - may progress
Often responsive to corticosteroids, sx excision

Best one to get

Lymphoma Dx and Tx

Antemortem Dx difficult
Excisional biopsy, fluid analysis
Bone marrow
Other
Tx: Corticosteroids, immunomodulation, antiviral medication, chemo (transient remission possible, recurrence typical)
Long term prognosis poor

Equine leukemia basics

Primary originats from bone marrow
Secondary is leukemic phase of lymphoma

Myeloid or lymphoid cell lineage
Leukemic: profound leukocytosis
Subleukemic: blast cells, low/normal WBC
Aleukemic: abnormal bone marrow only

Grave prognosis

Equine leukemia CS

Weight loss
anorexia
lethargy
Pyrexia
Lymphademopathy if secondary to lymphoma

Equine leukemia hematologic changes

``` Anemia Thrombocytopenia Marked leukocytosis Pancytopenia - Neutropenia, lymphopenia Increased blast or atypical cells in blood Hyperproteinemia Hyperfibrinogenemia ```

Equine leukemia Dx

Bone marrow aspirate Flow cytometry IHC, immunophenotyping

Equine myeloma

``` Plasma cell proliferation Primary: bone marrow Secondary: extramedullary - LN, spleen, kidney, liver Multiple myeloma: bone marrow and tissues ```

Equine myeloma CS

Weight loss, fever, lethargy Pale MM Limb edema Recurrent infection

Equine myeloma Dx

Bone marrow: plasmacytosis Hematology: anemia, hyperproteinemia (globulins), Pancytopenia (myelopathies), hypercalcemia, monoclonal immunoglobulinemia Poor prognosis, rapid deterioration

Equine erythron

``` Variable PCV - ~30% circulating equine RBC in spleen - Excitement/pain - transient increase in PCV - alpha 2 agonists - transient decrease in PCV Rouleau Peripheral reticulocytes extremely rare Howell Jolly Bodies - Basophilic nuclear remnants ```

Clinical evaluation of erythron

Coomb's test: detect Ig or complement on erythrocyte surface - Agglutination = positive - Useful with IMHA RBC fragility Bone marrow eval: Aspirate or core biopsy, characterize anemia (Regen, nonregen, NO circulating reticulocytes), myeloid:erythroid (

Anemia

Decreased O2 carrying capacity of blood secondary to RBC loss - hypoxia Causes: blood loss, hemolysis, impaired RBC production CS vary: tachycardia, tachypnea, depression, mucosal pallor/icterus, hemoglobinuria, lethargy, weakness

Anemia Dx

``` Hx PE CBC Urinalysis Bone marrow aspirate ```

Acute blood loss: hemorrhage

Causes: trauma, Sx, guttural pouch mycosis, hemorrhage into body cavity, peripartum hemorrhage, coagulopathy, neoplasia CS: Hypovolemic shock, colic and abd distension, dyspnea, braced stance, epistaxis

Acute blood loss Dx

PCV/TP decrease over 12-24h, with IMHA TP shouldn't decrease Blood lactate increases secondary to tissue hypoxia US Abdominocentesis, thoracocentesis

Acute blood loss Tx

``` Stop hemorrhage Address hypovolemic shock Judicious use of sedation Replace blood loss With internal hemorrhage body can reuse blood components- avoid removal if posiible ```

Blood transfusion basics

Transfused RBC last 2-4d in adult horse Cross match -Major: donor RBC- recipient serum alloAb - Minor: dono serum Ab - recipient RBC If cross match not possible Qa, Aa neg geldings or maiden mares

Blood transfudsion strategy

Replace 20-40% of total loss Can safely remove 5-10L from donor Avoid adverse rxn to transfused RBC (start slow) CS of adverse rxn: tachycardia, urticaria, dyspnea, pyrexia, colic, diarrhea, anaphylaxis, pulmonary edema, hemolysis, DIC

Causes of chronic blood loss

GI or urogenital/renal dz: neoplasia, EGUS, RDC, Hemostatic dysfunction Physiologic adaptation to gradual onset of tissue hypoxia secondary to anemia Iron stores may become depleted: low serum iron, decreased bone marrow iron stores, increased total iron binding capacity, hypochromic, microcytic anemia