C h a p t e r 1 1
Disorders of White Blood Cells and Lymphoid Tissues
243
Many cytokines derived from lymphocytes or bone
marrow stromal cells stimulate the growth and produc-
tion of new blood cells. Several members of this family
are called
colony-stimulating factors
(CSFs) because
of their ability to promote the growth of hematopoi-
etic cell colonies in the laboratory. The CSFs that act
on committed progenitor cells include erythropoietin
(EPO); thrombopoietin (TPO);
granulocyte-monocyte
colony-stimulating factor
(GM-CSF), which stimulates
progenitors for granulocytes, monocytes, erythrocytes,
and megakaryocytes;
granulocyte colony-stimulating
factor
(G-CSF), which promotes the proliferation of
neutrophils; and
macrophage colony-stimulating fac-
tor
(M-CSF), which induces macrophage colonies.
3–5
Other cytokines, such as the interleukins, interferons,
and tumor necrosis factor, support the proliferation
of stem cells and the development of lymphocytes
and act synergistically to aid the multiple functions of
the CSFs.
The genes for most hematopoietic growth factors
have been cloned and their recombinant proteins have
been generated for use in a wide range of clinical condi-
tions. The clinically useful factors include EPO, G-CSF,
and GM-CSF.
5
They are used for treatment of bone mar-
row failure caused by chemotherapy or aplastic anemia,
the anemia of kidney failure and cancer, hematopoietic
neoplasms, infectious diseases such as acquired immu-
nodeficiency syndrome (AIDS), and congenital and
myeloproliferative disorders. Growth factors are used
to increase peripheral stem cells for transplantation
and to accelerate cell proliferation after bone marrow
engraftment.
Leukocytes (White Blood Cells)
The leukocytes or white blood cells, which are the focus
of this chapter, originate in the bone marrow and cir-
culate throughout the lymphoid tissues of the body.
Leukocytes are commonly classified into two groups
based on the presence or absence of specific prominent
granules in their cytoplasm.
1,2
Those containing specific
granules (neutrophils, eosinophils, basophils) are classi-
fied as
granulocytes,
and those that lack granules (lym-
phocytes and monocytes) as
agranulocytes
(Fig. 11-2).
The granulocytes and the agranular monocytes/macro-
phages are derived from the myeloid stem cells in the
bone marrow and circulate in the blood (see Fig. 11-1).
The lymphocytes originate from lymphoid stem cells in
the bone marrow and migrate between the blood and the
lymphatic system.
Granulocytes
Granulocytes are spherical and have distinctive multilo-
bar nuclei. They are all phagocytic cells that are identifi-
able because of their cytoplasmic granules. They have
two types of granules:
specific granules
that bind neu-
tral, basic, or acidic dye components, and
azurophilic
A
Neutrophil
Nucleus
Erythrocyte
B
Eosinophil
Erythrocyte
Granules
Nucleus
C
Basophil
Nucleus
Granules
Granulocytes
Agranulocytes
D
Lymphocyte
Platelet
Nucleus
Erythrocyte
E
Monocyte
Erythrocyte
Nucleus
FIGURE 11-2.
White blood cells. Granulocytes
(A–C)
and agranulocytes
(D, E)
.
(A)
The neutrophil
has a large, segmented nucleus.
(B)
The eosinophil has many bright red–staining granules.
(C)
The
basophil has large dark blue–staining granules.
(D)
The lymphocyte has a large undivided nucleus.
(E)
The monocyte is the largest of the leukocytes. (From Cohen BJ. Memmler’sThe Human Body in Health
and Disease. 11th ed. Baltimore, MD:Wolters Kluwer Health
ǀ
LippincottWilliams &Wilkins; 2009:284.)
