CHAPTER 10
Lymphoid System
193
CLINICAL CORRELATION
Figure 10-12C.
Hodgkin Lymphoma.
H&E,
3
824
Hodgkin lymphoma
, also known as
Hodgkin disease
,
is one of the two major categories of malignant lym-
phoid cancers, characterized by painless enlargement of
lymph nodes, spleen, and liver. Patients often experi-
ence fever, night sweats, unexpected weight loss, and
fatigue. The cancer cells are transformed from normal
lymphoid cells, which reside predominantly in lym-
phoid tissues. Characteristic
Reed-Sternberg cells
, of
B cell origin, can be found in affected lymphoid tis-
sues. These cells are large (20–50
μ
m) and contain
abundant,
amphophilic
, and F
nely granular/homoge-
neous cytoplasm with two mirror-image nuclei (“owl’s
eyes”), each with an eosinophilic nucleolus and a thick
nuclear membrane. Radiotherapy and chemotherapy
are both effective in treatment of Hodgkin lymphoma.
The 5-year survival rate is approximately 90% when
the disease is detected and treated early.
C
Reed-Sternberg
cell
Lymphocyte
Figure 10-12A.
High endothelial venules (HEVs), paracor-
tex of lymph node.
H&E,
3
272; inset
3
720
Arteries that serve a lymph node enter the hilum and give rise
to branches that pass through the medulla and reach the cortex
where they form a network of capillaries in the nodule (fol-
licle) region. Postcapillary venules (in the paracortex region)
carry blood from the capillary bed back to the venule system
and out of the lymph node at the hilum (±ig. 10-10).
HEVs
are specialized postcapillary veins, which are lined by
cuboidal
cells
instead of squamous endothelial cells. The apical surfaces
of these cuboidal cells contain rich glycoproteins that attract
lectinlike receptors (L selectin) on the surface of the lympho-
cytes, which helps lymphocytes stop and attach to the HEVs.
Lymphocytes pass through HEVs by way of
diapedesis
and
enter the lymph node from blood circulation. The
inset
shows
a lymphocyte escaping from a HEV into the lymphatic tissue.
Cubodial
Cubodial
cell
cell
Lymphatic tissue
Lymphatic tissue
Lymphatic tissue
Lymphatic tissue
High
High
endothelial
endothelial
venule
venule
High
High
endothelial
endothelial
venule
venule
Lymphatic tissue
Lymphatic tissue
High
endothelial
venule
Cuboidal
cell
High
endothelial
venule
A
Active
Active
macrophages
macrophages
High
High
endothelial
endothelial
venules
venules
Active
macrophages
High
endothelial
venules
High endothelial
High endothelial
venule
venule
High endothelial
venule
Active
Active
macrophage
macrophage
Active
macrophage
B
Figure 10-12B.
High endothelial venules, paracortex of
lymph node.
H&E,
3
281; insets
3
725
HEVs
can be found in all of the secondary lymphoid organs
except the spleen. They are the major sites for both
naive B
and
T lymphocytes
that have migrated from circulation into the lym-
phatic tissue. After they enter the lymph node,
B cells
migrate to
the cortex region where they differentiate in the
germinal center
.
Most
T cells
remain in the
paracortex
region where they inter-
act with
antigen-presenting
cells
(
macrophages
). Once T cells
acquire antigens, they release cytokine (IL-4, IL-5, and IL-6),
which stimulates B cells’ division and maturation to become
memory B cells and plasma cells with the consequent produc-
tion of antibodies (±ig. 10-5A). Endothelial cells of HEVs are
cuboidal cells and have large round or oval nuclei with pale
chromatin. The
insets
show a lymphocyte in the cross section
of a
HEV
(
upper
); and an
active macrophage
in the paracortex
region (
lower
).
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