EXERCISES, LESSON 3
INSTRUCTIONS: Answer the following items by completing the statement or by writing
the answer in the space provided at the end of the item.
After you have completed all of these items, turn to "Solutions to Exercises" at the
end of the lesson and check your answers with the solutions.
Acquired immunity is the work of the body's l____d tissues. Lymphoid tissue can
be divided into two major groups: the c___l lymphoid organs and the p___l
lymphatic tissue. The central lymphoid organs consist of the b__e m___w and
t____s (and the fetal l___r). In these areas, s___m cells give rise to proliferating
and d______g l_______s through processes completely independent of antigen
stimulation. The peripheral lymphatic tissue includes lymph n____s, s_____n, and
g____t-associated lymphoid tissue.
One group of lymphocytes called (T) (B) cells are responsible for cellular i____y.
They are called this because they must be preprocessed in the t____s gland. The
other group, whose purpose is to form a_____s, is called (T) (B) cells.
While the major role of the bone marrow in adults is to replenish blood cells, it also
serves as a p______d environment in which T and B lymphocytes undergo
a____n-independent proliferation. Precursor T cells then move through the
bloodstream and pass through the walls of blood vessels to the t___s. They
rapidly proliferate within the gland and acquire new surface m____s. T cells pass
from the thymus to the blood and seed peripheral l___d tissue, where they begin
to function as i______tent T cells.
At the end stage of T cell differentiation, there are two distinct subsets of T cells:
(1) h____r (inducer) T cells, which express T_ and (2) s____sor (cytotoxic) T cells,
which express T_.
Maturation of B cells in humans takes place first in the f____l l____r and later in
the b___e m____w of the adult.
M___nal a____s can be used to detect B-specific markers. At various stages of
m____n, a B cell expresses unique m____s on its surface that are characteristic of
a particular d______tal stage.