CO3 Hemolymphatic

Question 1

Components of the hemolymphatic system:

Answer 1

• Thymus
• Spleen
• Bone marrow
• Lymph nodes
• All cells in blood:
  Granulocytes, lymphocytes, red blood cells, platelets, monocytes, etc.

Question 2

Conditions affecting the hemolymphatic system

Answer 2

1. Hypoplasia or atrophy (= immunodeficiency)
2. Hyperplasia (= immune reactivity)
3. Inflammation (lymphadenitis)
4. Infection
5. Neoplasia

Question 3

X-linked SCID in dogs- example of hypoplasia of the hemolymphatic system
- what occurs?

Answer 3

Naïve helper T- lymphocyte meets antigen
> production of cytokines to “help” B lymphocytes become plasma cells, and cytotoxic lymphocytes become “killer” cells
(IL2, 4, 7, 9, 15)
> product is cytotoxic lymphocytes and plasma cells
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In X-linked SCID in dogs, the helper T-cell is not able to signal to B-cells and cytotoxic lymphocytes, so they do not differentiate into full-grown immune cells
> a mutation that impairs cytokine signals that are necessary for lymphocytes to respond to antigens

Question 4

How would a dog with SCID present clinically?

Answer 4

-puppy
- opportunistic infections
- gender (male more likely)
- undetectable lymph nodes

Question 5

What lab tests would confirm SCID in a dog?

Answer 5

• lymphopenic - no puppy should have this
• low globulins

Question 6

difference between a normal lymph node and one from a dog with SCID?

Answer 6

• no lymphocytes in SCID
  > undetectable lymph nodes

Question 7

SCID in horse - how does this arise?

Answer 7

The condition is due to inability to recombine genes necessary to generate functional receptors on lymphocytes
> As a result, affected animals have neither the ability to produce antibodies (B lymphocytes) nor the ability to kill virus-infected cells (CD8+ cytotoxic T cells) nor can they generate helper cytokines (CD4+ helper T cells)

Question 8

is lymphoid hypoplasia common in animals?

Answer 8

no - lack of lymphocytes is incompatible with life

Question 9

types of reactive lymphoid hyperplasia

Answer 9

= the immune system hard at work!
* follicular hyperplasia - B cells
* paracortical hyperplasia - T cells
* sinus histiocytosis - macrophages, et al.

> In general, all elements occur simultaneously

Question 10

gross clinical finding for reactice lymphoid hyperplasia

Answer 10

palpably enlarged lymph nodes

Question 11

what is cloncal expansion, and how does it result in an enlarged lymph node

Answer 11

A very active immune response often manifests with palpably enlarged lymph nodes due to B cell activity (follicular hyperplasia), T cell activity (parafollicular hyperplasia) and/or macrophage hyperplasia (sinus histiocytosis). In general, all elements occur simultaneously, and a lymph node is enlarged because antigen-specific cells divide (hyperplasia) and are larger than resting lymphocytes (hypertrophy). This process is called clonal expansion, and results in enlargement of the node

Question 12

is the causative organism necessarily present in a reactive lymph node? what about neutrophils and eosinophils?

Answer 12

In reactive lymphoid hyperplasia the causative organism may not present in the lymph node, but rather microbial components have been phagocytosed by macrophages at tissue sites, and are being presented as processed antigens to lymphocytes in the lymph node. Thus, “primary” inflammatory cells such as neutrophils or eosinophils may not be present in enlarged lymph nodes.

Question 13

Cytologic examination of a lymph node aspirate in reactive lymphoid hyperplasia yields what?

Answer 13

Cytologic examination of a lymph node aspirate does not yield architectural information, but rather a somewhat “haphazard” mixture of cells from various sites within the node. Since the follicles comprise the majority of a hyperplastic node, plasma cells (mature B cells) are typically prominent. Thus, the picture of lymphoid hyperplasia consists of a mixture of cells with small resting lymphocytes, large lymphoblasts, plasma cells, and macrophages. Long- standing lymphoid hyperplasia may result in the formation of Russell bodies (immunoglobulin accumulated in the endoplasmic reticulum of plasma cells).

Question 14

Splenomegaly due to lymphoid hyperplasia occurs in what type of infections?

Answer 14

systemic infections, in particular those that have a blood-borne phase

Question 15

causes for spleen enlargement other than blood-borne systemic infection

Answer 15

extramedullary hematopoiesis, congestion, neoplasia, or excessive phagocytic activity (i.e. immune hemolytic anemia).

Question 16

what happens to lymphocyte populations after exposure to an antigen that leaves us with memory lymphocytes?

Answer 16

• clonal expansion of antigen specific lymphocytes
• apoptosis of effector lymphocytes
• generation of memory lymphocytes

Question 17

albumin and globulins acute phase response

Answer 17

• albumin down
• globulins up

=> response to inflammatory cytokines

Question 18

enlarged lymph nodes with neutrophils means what?

Answer 18

septic supprative inflammation, most likely
> Septic suppurative/pyogranulomatous lymphadenitis

Question 19

common causes of bacterial lymphadenitis in horses

Answer 19

Streptococcus, Rhodococcus, Actinomyces,
Corynebacterium, other bacteria

Question 20

what do we do if FNA an enlarged lymph node and find supprative inflammation?

Answer 20

bacterial culture to identify the organism and appropriate antimicrobial therapy

Question 21

Anaplasmosis (ehrlichiosis) acute, subclinical, and chronic disease presentations

Answer 21

1. Acute disease = 1-3 weeks after infection, replication in leukocytes > enlarged spleen & lymph nodes, anemia, malaise
2. Subclinical disease = months to years, organism restricted to spleen and difficult to find, dog fairly “normal”
3. Chronic disease = weight loss, neurological signs, cytopenia, edema, hyperglobulinemia, etc.

Question 22

Ehrlichia canis
- what species, cell, and tick are involved?

Answer 22

dogs, monocytes, brown dog tick

Question 23

Ehrlichia ewingii
- what species, cell, and tick are involved?

Answer 23

dogs, granulocytes, lone star tick (SW
US)

Question 24

Anaplasma (Ehrlichia) platys
- what species, cell, and tick are involved?

Answer 24

– dogs, platelets, brown dog tick

Question 25

Anaplasma phagocytophilum (old E. equi and E. phagocytophilia) –
- what species, cell, and tick are involved?

Answer 25

dogs, granulocytes, deer tick

Question 26

Neorickettsia (Ehrlichia) risticii –
what species, cell, and disease?

Answer 26

horse, monocytes, Potomac horse fever

Question 27

What is lymphadenititis? how does it occur and what cells will we see? gross observations?

Answer 27

Infection of the lymph nodes may occur with some bacterial or fungal organisms that have overwhelmed defense mechanisms at the site of entry. Typically, this results in an infiltrate of cells of the innate defense system, such as neutrophils and macrophages, into the lymph node. As a result, the lymph node is enlarged, tender, and the animal is frequently pyrexic. In severe cases, abscessation of the lymph node may result in rupture of the node with drainage into a body cavity or through the skin.

Question 28

microscopic lymphadenitis observations

Answer 28

Microscopically, lymphadenitis is characterized by large numbers of neutrophils (with most bacterial infections) or macrophages (some bacteria, most fungi and protozoa).

Question 29

an aspirate from a lymph node with lymphadenitis consists of:

Answer 29

• a mixture of lymphocytes (since specific immunity has been stimulated), neutrophils, macrophages (and occasionally eosinophils), and generally the causative organism can be seen.

Question 30

aspirates from normal lymph nodes have what proportion of primary inflammatory cells?

Answer 30

In aspirates from “normal” lymph nodes, the primary inflammatory cells comprise less than 5% of all cells (unless there is a lot of iatrogenic hemorrhage with blood neutrophils).

Question 31

lymphocyte life-span and movement

Answer 31

• Lymphocytes are long-lived, and continuously move between lymph nodes, spleen, and bone marrow in a highly organized fashion.
• They use receptors on endothelial cells specific for individual lymph nodes or organs, and for specific locations within each organ.
• Most lymphocytes reside in the lymph nodes and spleen, but small lymphoid aggregates are present in most organs though they may not form a discrete “node”.

Question 32

neutrophil and eosinophil lifespan

Answer 32

Neutrophils move from blood into tissues and die within a day, while eosinophils may persist for days in tissues

Question 33

monocyte lifestyle and life span

Answer 33

Monocytes come from the bone marrow, circulate for 1 to 2 days, and then move into the tissues where they become long-lived macrophages and antigen-presenting cells such as dendritic cells.

Question 34

platelet life span

Answer 34

~10 days

Question 35

RBC life span

Answer 35

Aged red blood cells are removed by splenic macrophages after a pre-determined lifespan of 60 days (cats) to 150 days (horses, cattle) in circulation.