1. MLAB 1415- Hematology Keri Brophy-Martinez
Chapter 20:
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. Characteristic Cell 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.

5. Antigen-stimulated lymphocytes pg. 129
Reactive or Atypical: Atypical is widely used; however, connotes abnormal or malignant
Downey Cell: obsolete term for reactive lymph and immunoblasts
Immunoblasts:
large cells with prominent nucleoli
fine clear chromatin
dark purple-blue cytoplasm
preparing for or engaged in mitosis in response to stimulus
Plasmacytoid lymphs:
daughters of B immunoblasts
Eccentric nucleus with moderate amount of deep blue cytoplasm
Plasma Cell
Fully differentiated B cell
Eccentric nucleus with “cartwheel appearance” with large amount of basophilic cytoplasm
Perinuclear clearing (Golgi apparatus)
Releases Ig

6. Reactive Lymph Characterisitcs
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

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

8. 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

9. 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”

10. Causes of Reactive Lymphocytosis
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 by receptor CD21 which causes it to express the activation marker CD23 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 lymphadenpathy
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)
Patients will often present with lethargy, headaches, fever, chills, sore throat, nausea. The classic triad of symptoms include fever, pharyngitis, and lymphadenopathy. The spleen can be enlarged in 50-75% of patients.
What causes the change in the cell? EBV attaches to B lymphocytes by means of a specific receptor designated CD21 on the B lymp membrane surface. This is also the receptor for a complement component. The binding of the virus to the lymph activates the lymph, causing it to express the activation marker CD23. This marker happens to be the receptor for B lymphocyte Growth factor. The virus has now told the cell to continue growing, thus the larger appearance of this type of cell. Once the virus gets inside the B cell, it is incorporated into the genome and instructs the host cell to begin production of EBV proteins. These VIRAL proteins are expressed on the B cells surface. This process immortalizes the EBV-lymphs. NK cells fight the infected cells as well as cytotoxic T cells. The majority of the REACTIVE LYMPHS seen in the peripheral blood are the suppressor-cytotoxic T Lymphs.

11. 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)

12. 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

13. 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

14. Causes of Reactive Lymphocytosis
Infectious lymphocytosis
Affects children
Viruses include adenovirus, coxsackie A and Bordetella pertussis
Leukocytosis and lymphocytosis occur in first week of illness then return to normal

15. Lymphocytopenia Absolute lymphocyte count< 1.0 x 109/L Causes
Decreased production or increased destruction of lymphocytes
Changes in lymphocyte circulation patterns
Corticosteroid therapy
Other unknown causes
Refer to page 411, table 20-4

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

17. 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

18. Congenital Deficiencies
Decrease in lymphocytes and impairment in either cell-mediated immunity (Tcells), humoral immunity(Bcells) or both
Lymphocytes appear normal on ps

19. Congenital Deficiencies
Severe Combined immunodeficiency Syndrome
Major qualitative immune defects involving both humoral and cellular immune functions
Fatal by 2 years if untreated by bone marrow transplant or gene therapy
Wiskott-Aldrich Syndrome
Patients have recurrent infections due to immunodeficiency (decreased CD8 T-lymphs), thrombocytopenia and eczema