1. MLAB 1415- Hematology Keri Brophy-Martinez
Nonmalignant Lymphocyte Disorders

2. Review Lymphs originate primarily from bone marrow and thymus
Secondary organs include spleen, lymph nodes, tonsils, and Peyer’s patches in GI tract

3. Review Pluripotent Stem cell Lymphocyte Stem cell B-cell T-cell
3 general populations
B- lymphs: %
T-lymphs: 60-80%
NK: < 10%

4. Introduction
Important to differentiate benign conditions associated with lymphocytosis from malignant lymphoproliferative disorders
How?
Presence of heterogeneous reactive lymphs
Positive serological test for antibodies against infectious organisms
Absence of anemia and thrombocytopenia
All of above favor a benign diagnosis

5. Introduction Majority of disorders affecting lymphocytes are acquired
Hallmark: reactive lymphocytosis
Reactive process
Congenital disorders
Defect is found within lymphocytic system

6. Lymphocytosis Excess of lymphocytes in the blood.
Absolute lymphocyte count (ALC) > 4.8 x 109 /L in adults
Relative count > 35-45%
Self-limited
Reactive process is due to infection or inflammatory conditions
B and T cells involved
Lymphocytes develop in response to antigenic stimulation. They become “activated”

7. “Activated” Lymphocytes
Reactive lymphocyte - transformed or benign lymph
Similar terms are transformed lymph, atypical lymph, virocyte, immunoblast, plasmacytoid, Downey cell
What causes them?
Once stimulated by infection or inflammatory condition, lymphs enter various stages of activation
Morphologically heterogeneous population presents signs of activation:
Large irregular shape
Cytoplasmic basophilia
Vacuoles
Azurophilic granules can be present and are thought to contain pore-forming proteolytic enzymes and serine proteases with pro-apoptotic activity.

8. Activated Lymph Characteristics
Normal Lymph
Size
9-30 µm
8-12 µm
N:C ratio
Decreased
High
Cytoplasm
Abundant
Colorless to dark blue
Azurophilic granules
Can scallop the RBCs
Scant
Colorless to light blue
Nucleus
Elongated, irregular
Round
Chromatin
Coarse to moderately fine
Coarse
Nucleoli
Absent to distinct
Absent

9. ID the Activated Lymphs..

10. Causes of Reactive Lymphocytosis
Infectious mononucleosis (IM)
Toxoplasmosis
Cytomegalovirus (CMV) Infection

11. Infectious mononucleosis (IM)
Caused by the Epstein-Barr Virus (EBV) which enters the body via saliva (“kissing disease”)
EBV Pathophysiology
EBV attaches to B lymphs causing the lymph to express an activation marker that stimulates B-lymphocyte growth factor.
The virus is incorporated into the lymph genome making the cell express viral proteins on the cell membrane and immortalizes the line of EBV-lymphs.
Activated cytotoxic T-lymphs are released to inhibit the activation and proliferation of EBV infected lymphs. These are the characteristic Reactive Lymphs.
Clinical symptoms
Classic triad: fever, pharyngitis and lymphadenopathy
Dysphagia (difficulty swallowing)
General malaise
Fatigue
Spleen is enlarged and nodes are firm but not tender or warm
Generally seen in children and young adults (14-24 yrs old)

12. Lab features of IM CBC Relative lymphocytosis
Peaks at 2-3 weeks of infection, remains elevated for 2-8 weeks
Leukocyte count x 109/L
Peripheral smear
Reactive lymphocytes , historically referred to as a Downey cell with irregular cytoplasmic border, increased cytoplasm and dark blue edge around the periphery of the cytoplasm.
>20% reactive lymphs
Serologic test
Heterophil antibody test (i.e Monospot)

13. Causes of Reactive Lymphocytosis
Toxoplasmosis
Infection with intracellular protozoan Toxoplasma gondii
Acquired infections in children and adults due to ingestion of oocysts from cat feces or undercooked meat
Can be transmitted via placenta

14. Causes of Reactive Lymphocytosis
Cytomegalovirus (CMV) Infection
Belongs to herpes family
Endemic worldwide
Acquired through transfusions, sexual contact and close contact
Can be transmitted across placenta
Poor prognosis for immunocompromised individuals who contract virus

15. Immune Deficiency Disorders
Impaired function of one or more of the components of the immune system: T, B, or NK lymphocytes
Decreased lymphocyte count
Body unable to mount an adaptive immune response
Can be acquired or congenital

16. Acquired Deficiencies
Acquired immune deficiency syndrome (AIDS)
Infection with a retrovirus, human immunodeficiency virus type-1 (HIV-1)
Transmission through sexual contact or contact with blood and/or blood products
Binds CD4 antigen on helper T lymphocytes which results in cell lysis