4. Lymphocytes - Peripheral Blood
In the previous image, the lymphocyte manifests the cytologic
features of a normal circulating lymphocyte: small size (about the
size of a red cell), high nuclear-to-cytoplasmic ratio (N/C) and
condensed nuclear chromatin. These small lymphocytes constitute about
90% to 95% of circulating lymphocytes. However, as the cells above
demonstrate, larger lymphocytes may also be seen in the peripheral
blood of normal individuals. These larger lymphocytes are given the
designation "atypical lymphocytes" -- to distinguish them from
"typical" small circulating lymphocytes -- and make up less than 5%
of lymphocytes in circulation. One "atypical" characteristic is the
frequent presence of nucleoli. Another "atypical" feature is the
presence of abundant blue cytoplasm. This blue hue sometimes is noted
only at the periphery of the cytoplasm. Lymphocytosis is found in
viral syndromes, such as infectious mononucleosis, although it is not
diagnostic of such infections. Frequently in these viral syndromes
there is an increased number of atypical lymphocytes. The circulating
atypical lymphocytes in these viral syndromes are T cells that have
been transformed (or activated) in response to EBV-infected B cells
in infectious mononucleosis. Are these activated lymphocytes mature
or immature (i.e., blasts)?
Answer
Copyright © 1999 by W. B. Saunders Company
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ISBN: 0-7216-8462-9
