b. Neutrophils. Neutrophilic leukocytes are excellent microphages. That is,
they engulf bacteria and other microscopic particles. The particles are first surrounded
by cellular pseudopodia and then incorporated into a cell vacuole. There the foreign
bodies mix with substances released from the cytoplasm of leukocytes. In this way the
leukocyte is not injured by whatever "combat activity" is taking place in the vacuole.
Neutrophils are fully developed (mature) cells that are incapable of mitotic division.
They carry on active metabolism. Eventually the granulocytes disintegrate and in
inflammatory processes are succeeded by monocytes.
c. Eosinophils. The eosinophils are easily distinguishable by their large
cytoplasmic granules. They have some similarities with the neutrophil: they arise from
a common stem cell and share same morphologic features. Unlike the neutrophil,
however, eosinophils initially develop in the bone marrow, then are released into the
circulation, and undergo further maturation in the spleen. Their emergence from the
marrow seems to depend upon a stimulus provided by lymphocytes. Eosinophils are
found in tissue fluid as well as in peripheral blood, especially in areas where there is an
allergic reaction. Current thinking holds that eosinophils are involved in antigen-
antibody reactions, and have been shown to phagocytize antigen-antibody reactants.
Eosinophils are also thought to transport, or at least contain, lysins that act on fibrin. It
is suggested that eosinophils limit the action of substances such as histamine. How this
is accomplished is not yet clear. The mobilization of eosinophils from their reserve in
the bone marrow is at least in part under hormonal control. If the adrenal cortex is
functioning properly, an injection of adrenocorticotropic hormone (ACTH) results in a
marked decrease in the number of circulating eosinophils and in the number of
circulating lymphocytes. On the other hand, there is an increase in the number of
d. Basophils. The function of basophils in man has not been ascertained.
They quite possibly represent a vestige of evolution. Their granules have been found to
contain heparin and these cells frequently appear during the clot dissolution phase of an
injury. Hence, it has been suggested they may be involved in clot absorption.
e. Lymphocytes. The lymphocyte is now believed to be directly connected with
antibody production. Undoubtedly, the lymphocyte performs important immunologic
functions. According to very recent studies, many of the activities previously thought to
take place in the reticuloendothelial (RE) system actually take place in lymphocytic
Platelets possess metabolic system, expend energy, and respond to stimulus.
They contain many enzymes and undergo respiratory activity and glycolysis. They
possess coagulation factors usually designated as PF-1, PF-2, and on through PF-7.
The cells contain fibrinogen and vasoconstrictor substances, calcium, and many other
components that are either known or presumed to participate in the clotting mechanism.
Clot-promoting lipoproteins are also found in platelets. In addition, well-defined