Chapter 15
White Blood Cell Disorders
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White Blood Cell Disorders
► In
Chapter 15, you will be introduced to the
various disorders of leukocytes. Included in
this chapter will be a discussion on the
kinetics and functions of neutrophils,
disorders of neutrophils, and other
morphologic changes of neutrophils. The
function and morphology of lymphocytes
will also be covered. Diseases that affect
lymphocytes are discussed.
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Circulating Kinetics and Morphology
of Neutrophils
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► Granulocytes
are divided into three subsets:
 Neutrophils
 Basophils
 Eosinophils
► Neutrophils
are phagocytic cells.
► They are capable of movement from the
circulatory system into the tissues to engulf
and destroy bacteria.
► They mobilize to sites of infection and play a
role in the inflammatory response.
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Circulating Kinetics and Morphology
of Neutrophils
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► Two
types of granules:
 Primary or azurophilic
 Secondary or specific
► All
granules contain enzymes which are
involved in killing and digesting bacteria and
fungi.
► Neutrophils are very mobile cells.
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Circulating Kinetics and Morphology
of Neutrophils
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► Once
in the circulatory system, the neutrophils
divide up into two pools:
 Marginating pool: These neutrophils remain in the
circulatory system searching for an area of
inflammation. When inflammation is found, these
neutrophils leave the circulatory system by process of
diapedesis and enter surrounding tissues.
 Circulating pool: Leave the blood stream by random
migration and do not return to the bloodstream.
► Neutrophils
are believed to survive 2-5 days after
entering the tissues.
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Neutrophil Counts in Peripheral
Blood
► Variations
in the numbers of neutrophils is a
useful diagnostic tool; Variations reflect
response of neutrophils to underlying
disease (i.e. bacterial infection) or of
another disorder such as leukemia.
► Normal ranges vary widely with age:
 Newborns may have more WBCs
 Babies may have more lymphocytes
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Response to Infections
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Neutrophils play central role in fighting infections and
inflammatory agents. Can reach area of inflammation
within minutes by migrating (diapedesis) from circulatory
system to site of infection.
► Neutrophilia is increase in relative number of neutrophils
in response to infection or inflammatory process.
Accelerated release from bone marrow seen as "shift to
left" which is defined as increased number of
metamyelocytes and bands in peripheral blood. Rarely see
more immature neutrophil forms in infections (will see
more immature forms in leukemia).
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Response to Infections
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In addition to changes in neutrophil number, will see
morphologic changes such as toxic granulation, Dohle
bodies, and cytoplasmic vacuoles:
 Toxic granulation: granules become larger and stain more
darkly. Granules tend to be primary granules that are peroxidase
positive. Frequently seen in severe infections.
 Dohle bodies: pale blue cytoplasmic inclusions. Seen on
periphery of cell. Consist of few strands of rough endoplasmic
reticulum that have banded together.
 Vacuoles: Neutrophils may develop vacuoles in cytoplasm. May
see ingested microorganisms as well.
►
Presence of any of these changes may suggest progression
toward sepsis; however, are not specifically related to
infections. May see in massive trauma, during pregnancy,
in inflammatory responses, and in drug reactions.
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Neutrophil
Function
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Neutrophil Function
► Main
function is destruction of
microorganisms through process called
phagocytosis.
► Once bacteria infiltrate tissues, neutrophils
immediately respond. Phagocytosis begins.
► Phagocytosis consists of three phases:
 migration and diapedesis
 opsonization and recognition
 ingestion, killing, and digestion
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Migration and Diapedesis
Phase 1
► Neutrophils
are attracted to the area by
chemical signals produced by inflammation,
injury, and infectious agents.
► Chemotaxis is the movement of
neutrophils towards the chemoattractant.
► Neutrophils migrate from the vessels by
diapedesis between the endothelial cells of
the vessels, and migrate towards the
chemoattractor.
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Opsonization and Recognition
Phase 2
► Neutrophils
cannot recognize or attach to
microorganisms. They need help.
► Opsonization is process which facilitates
recognition and attachment of neutrophil to
organism. Marks organism for ingestion by
neutrophil.
► As chemotaxis occurring, immunoglobulins and
complement components coat surface of
bacteria. Marked bacteria (opsonin) easily
recognized by neutrophil and ingested.
► Ingestion requires presence of membrane-bound
immunoglobulin.
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Ingestion, Killing and Digestion
Phase 3
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► Ingestion
begins as soon as organism and
neutrophil bind together. Membrane pseudopods
surround organism, forming isolated vacuole
within cytoplasm of neutrophil. Called a
phagosome.
► Simultaneously, cytoplasmic granules migrate to
and fuse with phagosome, forming a
phagolysosome.
► Once phagolysosome formation complete,
granules release contents. Ingested organism
exposed to lytic activity of granular enzymes that
leads to death of organism and its eventual
digestion.
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Ingestion, Killing and Digestion
Phase 3
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► In
the leukocyte, there are pH changes,
dumping of digestive enzymes into the
phagolysosome, production of hydrogen
peroxide and superoxides. These digestion
processes are collectively called
respiratory burst. These oxygen
metabolites injure the organism and interact
with other granular contents to produce
toxic agents such as hydrochloric acid
(household bleach).
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Neutrophil
Disorders
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Disorders of Neutrophils
► Neutrophil
disorders may be classified as
quantitative (abnormal numbers) or
qualitative (abnormal function).
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Quantitative Disorders of Neutrophils
► Leukocytosis:
an increase in the number
of WBCs.
► Leukopenia: a decrease in the number of
WBCs.
► Neutropenia: an absolute decrease in the
number of circulating neutrophils.
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Acquired Neutropenia
► Five
factors associated with acquired
neutropenia:
 Viral infections
 Ingestion of medications
 Alloantibody formation (from transfusion or
pregnancy, much like HDN)
 Autoantibody formation
 Secondary condition due to another process
(aplastic anemia, bone cancer)
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Qualitative Disorders of Neutrophils
► Involve
neutrophil function.
► Extremely rare occurrences.
► Classified according to major defect
expressed:




Cytoplasmic granules
Disturbance of respiratory burst
Chemotaxis
Combination of defects
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Chediak-Higashi Syndrome
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► Rare autosomal recessive condition.
► Features include recurrent bacterial infections,
partial albinism, and presence of giant lysosomal
granules in cells such as granulocytes, monocytes,
lymphocytes, and platelets. Mild bleeding
tendencies may occur.
► Have progressive neurologic complications during
childhood. Many patients die as result of infection
during childhood. Adults enter into accelerated
phase that progresses through pancytopenia,
organomegaly, systemic infections, and eventually,
death. Staphylococcus aureus primary cause of
infections.
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Chediak-Higashi Syndrome
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► **Have
inefficient and prolonged bacterial
killing. Release of lysosomal enzymes impaired by
abnormal granules. In Wright's stain, giant
granules more likely seen in lymphocytes (stain
deep purple to dark red).
► Management includes prophylactic antibiotic
treatment and high daily doses of ascorbic
acid. In cases of infection, aggressive intravenous
treatment required.
► Bone marrow transplant only hope of
cure. Should be performed before accelerated
phase begins.
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Chronic Granulomatous Disease
(CGD) 1 of 2
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Heterogeneous disorder of neutrophil that can be
chronic or intermittent.
**Attributed to failure in activation of respiratory burst
that results in little or no superoxide production.
Patients present with lymphadenitis, deep tissue
infections such as osteomyelitis, and visceral and
hepatic abscesses. Have frequent pulmonary
infections, organomegaly, and infected eczematoid
rashes.
Patients have neutrophilia rather than neutropenia.
Hallmark characteristic is formation of granulomas
during chronic inflammatory reactions that keep
organisms localized.
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Chronic Granulomatous Disease
(CGD) 2 of 2
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►
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May be inherited as either sex-linked-recessive or as
autosomal-recessive. Regardless of form, end result is
that superoxide can not be produced, and in turn,
bacterial killing is ineffective. Ingestion of bacteria,
degranulation, and phagolysosome formation normal.
Diagnosis made by demonstrating bactericidal defect
resulting from absence of respiratory burst on nitroblue
tetrazolium test (NTB), or by measuring respiratory burst
activity by flow cytometry.
Aggressive prophylactic antibiotic therapy begun as soon
as diagnosis made. Gamma interferon effective in
limiting frequency of infections. Granulocyte transfusions
useful. Bone marrow transplants beneficial in children.
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Hypersegmentation of Neutrophils
► Larger
than normal neutrophils (and
sometimes eosinophils) with six or more
nuclear lobes present.
► May be an indicator of megaloblastic anemia
or of benign autosomal recessive condition
called benign hypersegmentation of
neutrophils.
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Hyposegmentation of Neutrophils
► Characteristic
of Pelger-Huet anomaly.
► Nucleus is bilobed or lacks lobes altogether.
Nuclear chromatin excessively coarse and
condensed. Nuclei described as
"dumbbell" or "pince-nez" appearing
with two symmetric lobes being joined by
filament.
► True Pelger-Huet is autosomal-dominant
condition. Is benign condition.
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Cytoplasmic Changes
► Cytoplasmic
changes may also occur.
► Alder anomaly or Alder-Reilly inclusions:
 Presence of prominent, dark staining, coarse
granules in many or all cell lines. Prominent
granules are similar to toxic granulation, except
they are larger and permanent (not a transient
change cause by infection or toxins).
► May-Hegglin
anomaly:
 Demonstrates larger, blue-staining cytoplasm in
the granulocytes, resembling Dohle bodies.
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Lymphocyte
Disorders
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Lymphocyte Disorders
► Lymphocytosis:
An excess of lymphocytes
in peripheral blood.
► Reactive lymphocytes: Used to describe
transformed or benign lymphocytes. You
should use the term “reactive”, not
“atypical”. The word “atypical” is used to
describe malignant-appearing cells.
► A few reactive lymphocytes is not abnormal.
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Lymphocyte Morphology
► Lymphocytes
are supposed to vary in size;
In malignant disorders, the lymphocytes
appear the same size and shape because
they arise from the same monoclonal cell.
► Reactive lymphocytes:
 May have azurophilic granules
 Cytoplasm stains unevenly, with the peripheral
regions of the cytoplasm staining darker.
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Plasma Cells
► Plasmacytoid
lymphocytes (plasma cells)
have coarse, clumped nuclear chromatin, a
perinuclear halo, and an eccentric nucleus.
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Causes of Reactive Lymphocytosis
► Infectious
mononucleosis, which is caused
by the Epstein-Barr Virus (EBV), is most
commonly seen in young adults between
the ages of 17 and 25 years of age.
► Cytomegalovirus Infection (CMV), which
belongs to the herpes virus family, is usually
asymptomatic in immunocompetent
individuals.
► Other viral infections.
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Malignant Conditions
► The
lymphocytes seen in malignant
disorders, such as leukemia, may be
confused with reactive lymphocytosis.
► Malignant cells in leukemia have the same
appearance and, therefore, are
morphologically different from reactive
lymphocytes seen in reactive conditions.
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Laboratory
Examination
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Laboratory Examination
1 of 2
Tests include CBC, serology, and microbiologic
cultures. The most useful tests are still the CBC with
differential and serology tests.
► Proper evaluation of peripheral blood smear crucial for
correct diagnosis of absolute lymphocytosis - especially for
patients with infectious mononucleosis.
► Serology tests important, especially Monospot test for
infectious mononucleosis. A positive Monospot and a
differential with reactive lymphocytes diagnostic for
infectious mononucleosis in some labs.
► Further serology testing differentiates among variety of
viral infections.
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Laboratory Examination
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► Can
trace course of disease by testing for IgM and
IgG antibodies. IgM antibodies formed early in
infection, while IgG antibodies formed after a
couple of weeks. Periodic testing of antibody
titers can trace course of disease through acute
and convalescent phases.
► If malignancies suspected, lymphocytes may be
distinguished by immunophenotyping tests.
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