MLAB 1415: Hematology
Keri Brophy-Martinez
Leukocytes- The Lymphocytes
Part Three
Differentiation & Maturation


Develop from HSC (hematopoietic stem cell)
Common lymphoid progenitor cell (CLP) gives rise to
the committed precursor cells:
o
T lymphocytes (60-80% of lymph population)

o
B lymphocytes (10-20%)

o
Thymus
Bone marrow
Natural killer cells (NK) (~ 2 %)
•
Bone marrow or thymus
Lymphopoiesis

Primary lymphoid tissue
 Bone marrow, thymus, fetal liver

Secondary lymphoid tissue
◦ Lymph node, spleen, Peyer’s patches in intestine and mucosal
tissues such as tonsils
◦ Active immune response occurs in above tissues where
lymphs communicate and interact with antigen-presenting
cells, phagocytes and macrophages
Lymphocyte Population

Reference range= 1.0- 4.8 x 109/L

Lymphocytosis
◦ Increase in lymphocytes
◦ Absolute number exceeds 4.8 x 109/L

Lymphocytopenia
◦ Decrease in lymphocytes
◦ Absolute number of lymphocytes is <1.0 x
109/L
Lymphocytes: T cells
◦ Function
 Cellular immune response (they do not produce antibodies)
 Three subsets
 Helper T cells
 Instrumental in aiding B cells in antibody production
 Turn on immune reponse
 Effected by Human Immunodeficiency Virus (HIV)
 Suppressor T cells
 Act as a “thermostat” to shut off the system or keep it under control
 Cytotoxic T cells
 Destroy by lysis of target cells (such as tumor cells)
 Play a role in inflammatory response
 Host defense when stimulated by interferon against certain viruses
(cytomegalovirus - CM, and hepatitis) by killing the virally infected target
cell before the virus replicates
 Responsible for chronic organ graft rejection. (T cells have many unique
antigens on their cell surfaces, some of which are the HLA - human
lymphocyte antigen - markers. HLA markers are instrumental in chronic graft
rejection and that is why tissue typing is done to establish a good donor
match.)
Lymphocytes: B cells

Function
 Humoral immune response by transforming into
antibody-producing plasma cells
 Defense against encapsulated bacteria such as
Streptococci
 Mediate hyperacute organ rejection
Lymphocytes: Natural Killer (NK)
cells

Function
◦ Recognize and kill tumor cells
◦ Recognize and kill cells infected with a virus
Maturation sequence of lymphocytes

Lymphoblast
◦ Cell size: 10-18µm
◦ Cytoplasm
 Blue/scanty
 No granules, Auer rods are
never present
◦ Nucleus
 Purple, smooth chromatin
 Smudged
 Round, central or
eccentric
 1-2 nucleoli
◦ N:C ratio = 4:1
Maturation sequence of lymphocytes

Prolymphocyte
◦ Size: 9-18µm
◦ Cytoplasm
 Blue, scanty
 Usually granules are
absent, but a few
azurophilic granules may
be present
◦ Nucleus
 Purple, condensed
chromatin
 Round or indented,
eccentric
 0-1 nucleoli
◦ N:C ratio = 3:1
Maturation sequence of lymphocytes

Mature lymphocyte
◦ Normal adult value: 25-35%
 Cell size: 7-10µm (a typical
normal lymph has a nucleus
that is the size of a normal
RBC)
◦ Cytoplasm
 Light blue, scanty to
moderate
 Few azurophilic granules
may be present
◦ Nucleus
 Purple, dense, clumped
chromatin
 Round or indented,
eccentric
 No nucleoli
Lymphocyte Maturation sequence
Large lymphocytes versus monocytes
Size
◦ Large lymph: 12-15µm
◦ Mono: 15-18µm
 Nucleus
◦ Large lymph: clumped, condensed
◦ Mono: lacy, brainlike folds
 Granules
◦ Large lymph: large azurophilic, easy to count
◦ Mono: red, fine
 Cytoplasm
◦ Large lymph: clear to light blue color, may be indented by red cells
◦ Mono: “ground glass” appearance, projection of blunt pseudopod blebs

Large granular lymphocyte
Monocyte
Comparison of LGL and
Monocyte
Lymphocytic Variants
Varied appearance
 Depends on degree of activation
 Many names
◦ Reactive
◦ Transformed
◦ Variant
◦ Atypical
◦ Downey cell
 Nomenclature varies depending on individual
facilities

Lymphocytic Variants

Cause
◦ Caused by antigenic stimulants such as viruses, posttransfusion reactions and organ transplants

General characteristics
◦ Increased size due to DNA activity in the nucleus and
RNA activity in the cytoplasm
◦ Enlarged and/or monocytoid nucleus
◦ Variation in nuclear chromatin pattern
◦ Nucleus may contain 1-3 nucleoli
◦ Abundant, sometimes foamy or vacuolated cytoplasm
◦ Variation in cytoplasmic color - gray-blue to intense
blue
◦ Absence of granules in cytoplasm
Reactive lymphocytes
Plasma cells
• Function is the synthesis and excretion of antibodies
(immunoglobulins)
• Normally not present in the peripheral blood; comprise 2% of bone
marrow cells.
o EXCEPT in the disease called multiple myeloma, a disease of
uncontrolled production of immunoglobulins.
• End stage of the B lymphocyte
•
Appearance
o Size: 10-18µm
o Cytoplasm is dark blue with perinuclear halo and may contain vacuoles
indicating antibody synthesis
o Nucleus is round, eccentric, dark purple with dense clumped chromatin
•
Variant plasma cells
o Grape or Mott cell - cytoplasm completely filled with red, pink or
colorless globules called Russell bodies
o Flame cell - cytoplasm stains bright red-staining proteinaceous
material
Plasma cells
References
Carr, J. H., & Rodak, B. (2009). Clinical
Hematology Atlas. St. Louis: Saunders.
 Harmening, D. M. (2009). Clinical Hematology
and Fundamentals of Hemostasis. Philadelphia:
F.A Davis.
 McKenzie, S. B., & Williams, J. L. (2010). Clinical
Laboratory Hematology . Upper Saddle River:
Pearson Education, Inc.
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