Page 462 - Atlas of Histology with Functional Correlations

In humoral-mediated response, antigens induce B cells to transform into

plasma cells
Plasma cells, in turn, secrete specific antibodies to destroy antigens
In cell-mediated response, T cells are activated, release cytokines, stimulate
other T and B cells, bind to target cells, and destroy them

SPLEEN

Largest lymphoid organ with extensive blood supply; filters blood and serves

as a blood reservoir
Surrounded by a connective tissue capsule that divides it into red and white
pulp
White pulp consists of lymphatic nodules with a germinal center around a

central artery
T predominant in periarteriolar lymphatic sheets (PALS) around central
arteries
Red pulp consists of splenic cords and splenic (blood) sinusoids

Splenic cords contain macrophages, lymphocytes, plasma cells, and different
blood cells
Does not exhibit cortex and medulla but contains lymphatic nodules
White pulp is the site of immune response to blood-borne antigens

T cells surround the central arteries, whereas B cells are mainly in the
lymphatic nodules
APCs and macrophages are found in white pulp
Breaks down hemoglobin from worn-out erythrocytes and recycles iron to

bone marrow
Degrades heme from hemoglobin, which is then excreted in the bile
During fetal life is an important hematopoietic organ and in adults serves as
blood reservoir

THYMUS GLAND

Lobulated lymphoepithelial organ with dark-staining cortex and light-
staining medulla
Most active in childhood and has an important role early in life in immune
system development

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