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==Anatomy & Physiology==
[[Lymph Nodes - Anatomy & Physiology|See here]]
==Lymph node responses in disease (The Total Node Response)==
===reactive nodes===
*immunological response to antigens
*hyperplasia
*cell proliferation in cortex
:- germinal centre activity
:- multiplication of cells in thymus-dependent area (paracortex)
*accumulation of newly-formed plasma cells in medullary cords
*macroscopically
:- bulging white cortex which may almost obliterate the medulla
===lymphadenitis===
*true inflammation
*swollen due to
:- congestion
:- oedema
:- leukocyte (neutrophil) accumulation
*pyogenic organisms
:- abscessation can develop
:- there will be pus and necrosis in the node itself
*lymphangitis: inflammation of lymphatics
==Role of the Lymph Node in Inflammation==
''Back to [[Inflammation - Pathology]]
* Antigenic material is transported in phagocytes via the tissue lymphatics to the local lymph node.
* In the subcapsular sinusoids of the lymph node, antigens are exposed to the reticular cell macrophages.
** These macrophages form a meshwork around the subcapsular, cortical and medullary sinusoids.
** These reticular cells present the antigen to the appropriate lymphocyte population.
*** To B-cells in the follicular centres
*** To T-cells in the parafollicular areas.
* When stimulated by antigen presentation, the respective areas undergo an increase in size by hperplasia.
** The lymphocytes produced later leave the lymph node to seek out the source of the antigen in the damaged portion.
* Bacteria surviving the initial local inflammatory reaction also travel to the lymph node.
** Travel either in macrophages or as a bacteraemia/septicaemia.
** In the lymph node, many bacteria are trapped, degraded and killed, or exposed to antibody produced by plasma cells in the medullary area.
** Bacteria set up an acute inflammatory response in the lymph node.
*** If they are pyogenic, baceria can produce abscessation in the lymph node.
**** E. g. Strangles.
***** An upper respiratory tract pathogen in the horse.
***** Abscesses in the cervical lymph nodes burst to the exterior.
***** Abscesses in the retropharyngeal node burst into the pharynx
***** Infection is usually localised to the head and neck, but can spread to cause abscessation elsewhere in the body.
===Bacteraemia===
* Bacteria may continue through the lymph nodes and circulate in the blood.
* These are generally cleared from the blood by other organs containing phagocytes.
** E.g. the [[Liver - Anatomy & Physiology|liver]], [[Spleen - Anatomy & Physiology|spleen]] and lungs.
* There are species differences in the ability to remove bacteria.
** In most species, the majority of clearance is carried out by the [[Liver - Anatomy & Physiology|liver]] and spleen.
** However, in the pig, the lung removes 60-80% of such bacteria.
===Septicaemia===
* Septicaemia is a condition where there are highly pathogenic bacteria circulating and rapidly multiplying in the blood.
** Accompanied by severe signs of clinical illness due to the liberation of bacterial toxins.
*** High fever
*** Rapid respiration
*** Shock
** Can result in the death of the animal.
====Gross Appearance====
* The lymph nodes, [[Liver - Anatomy & Physiology|liver]] and spleen are very hyperaemic and swollen.
====Histological Appearance====
* Capillaries in tissues taken immediately after death show bacteria in their lumens.
==Diseases Involving Reactive Nodes==
===Parasitic Diseases===
====bovine parasitic bronchitis====
====ostertagiasis====
====fascioliasis====
===Bacterial Diseases===
====clostridial====
==Diseases Involving Both Reactive Nodes and Lymphadenitis==
===[[Tuberculosis - Cattle]]===
===viz. brucellosis and Johne's disease===
* chronicity is caused by persistence of intacellular bacteria in lymph node macrophages
* Type IV hypersensitivity, but does not result in visible necrosis as in TB
===Johne's disease===
===Actinobacillosis===
===Actinomycosis===
===Equine strangles===
* acute inflammation
* produce pyogenic or necrotic foci in the drainage nodes
* involves submaxillary nodes
===Streptococcal adenitis or head gland disease===
* dogs
* acute inflammation as in above
==Diseases Parasitising the Lymphocytes==
*organism grows in the lymphocytes and ruptures them
*if large infecting dose
:- may be rapidly fatal since animal may no tb e able to mount an immunological attack
*if smaller infecting dose
:- loss of mature lymphocytes causes a dramatic stimulation of the remaining lymphocyte precursors
:- node hyperplasia follows
:- competition between lymphocytolysis by the organism and lymphocyte production by the nodes
:- clinically
::- may be swelling of the node at one stage and reduction in size at another
===canine distemper===
*virus
===swine fever===
*virus
===bovine east coast fever===
*protozoan
===[[Leishmania|Leishmaniasis in the dog]]===
==Other Lymphadenopathy==
===Lymph node pigmentation===
*Lungs
:- anthracosis
::- carbon derived from soot finds its way to the local nodes in macrophages
*Skin
:- dermatopathic lymphadenopathy or melanic reticulosis
::- in pigmented animals, especially black dogs
::- chronic inflammatory skin conditions lead to melanin deposition in hyperplastic nodules
:- also occurs in nodes draining skin melanomas where the pigment may be the result of skin ulceration or secondary tumour deposit
::- these two should not be confused since the prognosis is very different following surgery
===Emphysema===
*interstitial emphysema
:- common in cases of dyspnoea
:- more commonly affects bovine lung
::- due to well developed pulmonary lobulation and hence much loose interstitial lung tissue
*collection of gas bubbles in bronchial and mediastinal lymph nodes
:- gas travels to these nodes after gaining entry to the many lymphatic vessels present in the interstitial tissue
===Neoplasia===
* Primary tumours
** Lymphosarcoma (lymphoma)
:- of lymphoid cells with lymph node enlargement
:- smooth, pale hemogenous but may have areas of necrosis
:- may cause [[Parathyroid Glands - Pathology#Pseudo-Hyperparathyroidism|pseudo-hyperparathyroidism]]
* Secondary tumours
:- nodes often involved in the spread of tumours by extension or metastasis
:- usually carcinomas
==Haemal Lymph Nodes==
*ruminants only
*small; dark red/brown
*develop during foetal life
:- lymph node primordia which lose their lymph vessles
:- receive all cells and antigen from the BLOOD
*functional significance unclear
*probably respond to blood-borne antigen
[[Lymph Nodes - Anatomy & Physiology|See here]]
==Lymph node responses in disease (The Total Node Response)==
===reactive nodes===
*immunological response to antigens
*hyperplasia
*cell proliferation in cortex
:- germinal centre activity
:- multiplication of cells in thymus-dependent area (paracortex)
*accumulation of newly-formed plasma cells in medullary cords
*macroscopically
:- bulging white cortex which may almost obliterate the medulla
===lymphadenitis===
*true inflammation
*swollen due to
:- congestion
:- oedema
:- leukocyte (neutrophil) accumulation
*pyogenic organisms
:- abscessation can develop
:- there will be pus and necrosis in the node itself
*lymphangitis: inflammation of lymphatics
==Role of the Lymph Node in Inflammation==
''Back to [[Inflammation - Pathology]]
* Antigenic material is transported in phagocytes via the tissue lymphatics to the local lymph node.
* In the subcapsular sinusoids of the lymph node, antigens are exposed to the reticular cell macrophages.
** These macrophages form a meshwork around the subcapsular, cortical and medullary sinusoids.
** These reticular cells present the antigen to the appropriate lymphocyte population.
*** To B-cells in the follicular centres
*** To T-cells in the parafollicular areas.
* When stimulated by antigen presentation, the respective areas undergo an increase in size by hperplasia.
** The lymphocytes produced later leave the lymph node to seek out the source of the antigen in the damaged portion.
* Bacteria surviving the initial local inflammatory reaction also travel to the lymph node.
** Travel either in macrophages or as a bacteraemia/septicaemia.
** In the lymph node, many bacteria are trapped, degraded and killed, or exposed to antibody produced by plasma cells in the medullary area.
** Bacteria set up an acute inflammatory response in the lymph node.
*** If they are pyogenic, baceria can produce abscessation in the lymph node.
**** E. g. Strangles.
***** An upper respiratory tract pathogen in the horse.
***** Abscesses in the cervical lymph nodes burst to the exterior.
***** Abscesses in the retropharyngeal node burst into the pharynx
***** Infection is usually localised to the head and neck, but can spread to cause abscessation elsewhere in the body.
===Bacteraemia===
* Bacteria may continue through the lymph nodes and circulate in the blood.
* These are generally cleared from the blood by other organs containing phagocytes.
** E.g. the [[Liver - Anatomy & Physiology|liver]], [[Spleen - Anatomy & Physiology|spleen]] and lungs.
* There are species differences in the ability to remove bacteria.
** In most species, the majority of clearance is carried out by the [[Liver - Anatomy & Physiology|liver]] and spleen.
** However, in the pig, the lung removes 60-80% of such bacteria.
===Septicaemia===
* Septicaemia is a condition where there are highly pathogenic bacteria circulating and rapidly multiplying in the blood.
** Accompanied by severe signs of clinical illness due to the liberation of bacterial toxins.
*** High fever
*** Rapid respiration
*** Shock
** Can result in the death of the animal.
====Gross Appearance====
* The lymph nodes, [[Liver - Anatomy & Physiology|liver]] and spleen are very hyperaemic and swollen.
====Histological Appearance====
* Capillaries in tissues taken immediately after death show bacteria in their lumens.
==Diseases Involving Reactive Nodes==
===Parasitic Diseases===
====bovine parasitic bronchitis====
====ostertagiasis====
====fascioliasis====
===Bacterial Diseases===
====clostridial====
==Diseases Involving Both Reactive Nodes and Lymphadenitis==
===[[Tuberculosis - Cattle]]===
===viz. brucellosis and Johne's disease===
* chronicity is caused by persistence of intacellular bacteria in lymph node macrophages
* Type IV hypersensitivity, but does not result in visible necrosis as in TB
===Johne's disease===
===Actinobacillosis===
===Actinomycosis===
===Equine strangles===
* acute inflammation
* produce pyogenic or necrotic foci in the drainage nodes
* involves submaxillary nodes
===Streptococcal adenitis or head gland disease===
* dogs
* acute inflammation as in above
==Diseases Parasitising the Lymphocytes==
*organism grows in the lymphocytes and ruptures them
*if large infecting dose
:- may be rapidly fatal since animal may no tb e able to mount an immunological attack
*if smaller infecting dose
:- loss of mature lymphocytes causes a dramatic stimulation of the remaining lymphocyte precursors
:- node hyperplasia follows
:- competition between lymphocytolysis by the organism and lymphocyte production by the nodes
:- clinically
::- may be swelling of the node at one stage and reduction in size at another
===canine distemper===
*virus
===swine fever===
*virus
===bovine east coast fever===
*protozoan
===[[Leishmania|Leishmaniasis in the dog]]===
==Other Lymphadenopathy==
===Lymph node pigmentation===
*Lungs
:- anthracosis
::- carbon derived from soot finds its way to the local nodes in macrophages
*Skin
:- dermatopathic lymphadenopathy or melanic reticulosis
::- in pigmented animals, especially black dogs
::- chronic inflammatory skin conditions lead to melanin deposition in hyperplastic nodules
:- also occurs in nodes draining skin melanomas where the pigment may be the result of skin ulceration or secondary tumour deposit
::- these two should not be confused since the prognosis is very different following surgery
===Emphysema===
*interstitial emphysema
:- common in cases of dyspnoea
:- more commonly affects bovine lung
::- due to well developed pulmonary lobulation and hence much loose interstitial lung tissue
*collection of gas bubbles in bronchial and mediastinal lymph nodes
:- gas travels to these nodes after gaining entry to the many lymphatic vessels present in the interstitial tissue
===Neoplasia===
* Primary tumours
** Lymphosarcoma (lymphoma)
:- of lymphoid cells with lymph node enlargement
:- smooth, pale hemogenous but may have areas of necrosis
:- may cause [[Parathyroid Glands - Pathology#Pseudo-Hyperparathyroidism|pseudo-hyperparathyroidism]]
* Secondary tumours
:- nodes often involved in the spread of tumours by extension or metastasis
:- usually carcinomas
==Haemal Lymph Nodes==
*ruminants only
*small; dark red/brown
*develop during foetal life
:- lymph node primordia which lose their lymph vessles
:- receive all cells and antigen from the BLOOD
*functional significance unclear
*probably respond to blood-borne antigen