Lymphoid Pathology Flashcards
Where are T cells produced?
Thymus
Where are B cells produced?
Species variation:
Bone marrow - primates, rodents
Ileal Peyer’s Patches - ruminants, pigs, horses
Bursa of Fabricius - birds
What are secondary lymphoid tissues?
Lymph nodes
Spleen
MALT - tonsils, BALT, GALT
Lymph circulation through the lymph node
Afferent LV > subscapular sinus > paratrabecular sinuses > medullary sinuses > subcortical sinuses > efferent LV
In which area of lymph nodes are B cells located?
Follicular areas
Medullary cords
In which area of lymph nodes are T cells located?
Parafollicular areas
Etiologies for lymph node enlargement of “lymphadenomegaly”
Lymphadenitis: infectious, immune, toxic
Neoplasia: primary or metastatic
Lymphoid hyperplasia: antigen stimulation, viral
3 viruses that can cause lymphoid hyperplasia
Malignant catarrhal fever
BLV
FIV
Lymphoid hyperplasia can be ____ or ___
Paracortical or follicular
Etiology for lymph node hypoplasia (general and specific)
Primary immunodeficiency: combined immunodeficiency (CID) in Arabian foals or X-linked CID in dogs (Bassets, JRTs, Welsh corgis)
Etiologies for lymph node atrophy
Viruses that replicate in lymphs and induce apoptosis/necrosis: canine distemper virus and canine parvovirus
Glucocorticoids
Chemo drugs, ionizing radiation, malnutrition, cachexia
Red pulp functions in spleen
Erythrocyte storage
Antigen removal
Hematopoiesis/erythropoiesis
Erythrocyte destruction
White pulp function in spleen
Acquired immunity
- Periarteriolar lymphoid sheaths = T cells
- Follicles = B cells
Etiologies for decreased spleen size (uncommon)
Immunodeficiency, senile atrophy, wasting/cachexia
Lymphoid necrosis alone isn’t enough to decrease size usually
Etiologies for a uniform splenomegaly that has a bloody consistency on cut section
Congestion - terminal (euthanasia assoc)
Torsion
Etiologies for a uniform splenomegaly that has a firm, non-bloody consistency on cut section
Bacteremia/septicemia Granulomatous splenitis Hemolytic anemia Lymphoma (or other lymphoid neoplasm) Extramedullary hematopoiesis Amyloidosis, storage disease
Etiologies for splenic nodules/masses that have a bloody consistency on cut section**
Hematoma Hemangioma/hemangiosarcoma Nodular hyperplasia with hyperemia Splenic infarct Incomplete splenic contraction (PM finding)
Etiologies for splenic nodules/masses that have a firm, non-bloody consistency on cut section
Nodular hyperplasia
Granulomatous splenitis, splenic abscess
Lymphoma (or other lymphoid neoplasm)
Metastatic neoplasm
Common sites for hemangiosarcoma in dogs
Spleen
Liver
Right atrum
Lung
Thymus function
Primary lymphoid organ responsible for T cell development and maturation
Thymus structure
Cortex: primitive and maturing lymphocytes
Medulla: thymic epithelial cells and Hassall’s corpuscles, myoid cells, interdigitating cells and dendritic cells, lymphocytes
Diseases associated with a small thymus
Thymic hypoplasia (CID)
Maturation and aging (involution)
Thymitis
Thymic atrophy (lymphocyte apoptosis/necrosis)
Etiologies for thymitis
Porcine circovirus 2
Epizootic bovine abortion
Salmonella poisoning in dogs
Etiologies for thymic atrophy
Viral: FeLV, FIV, canine distemper or parvovirus, EHV-1, feline panleukopenia
Glucocorticoids
Nutritional deficiency: starvation, zinc, protein
Toxins: lead, mercury, polychlorinated biphenyls
Diseases associated with a large thymic
Thymic hemorrhage (young dogs)*
Lymphoma
Thymoma (epithelial component is neoplastic)
Define lymphoproliferative disease
All neoplasms arising from lymphocytes
Define lymphoma
Malignant neoplasm of lymphocytes, infiltrates and destroys lymphoid tissue and other tissue
Define leukemia
Neoplasm of lymphocytes or hematopoietic cells arising from the bone marrow; bone marrow = primary site; circulating neoplastic lymphocytes can be a complication of lymphoma “lymphoma with leukemia”
What five ways can lymphoma be classified?
Anatomic Immunophenotypic Pattern Cytologic WHO
Lymphoma in dogs
Most common 5-11 y/o
Boxer and Scottish Terrier = higher incidence
Gamma herpesvirus associated with some B-cell lymphomas
Most common anatomic form of lymphoma in dogs (others listed in order)
Multicentric* Alimentary Thymic Cutaneous Other - solitary or specialized
Lymphoma in cats
Most common neoplasm of cats*
Young cats affected by FeLV (>50% are >5 y/o)
Most common anatomic form of lymphoma in cats (others listed in order)
Alimentary* (often FeLV d)
Thymic (often FeLV+)
Multicentric (often FeLV+)
Solitary (kidneys often)
Lymphoma in cattle
Relatively common, usually >2 yr
Most forms caused by BLV - persistent lymphocytosis in 30% infected
Anatomic forms of lymphoma in cattle from most to least common
Multicentric*: commonly in right atrium, may present with signs of CHF
Cutaneous
Thymic: 6-30 m/o, not assoc with BLV
Calf form: Holsteins = genetic predisposition, <6 m/o (generalized, BM, liver spleen)
Alimentary (rare)
Solitary (spinal canal)
Most common anatomic form of lymphoma in horses
Multicentric
