Download Leukocytes (White Blood Cells)

Leukocytes (White Blood Cells)
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These three types of cell are called the
polymorphonuclear cells.
They all have a granular appearance for
this reason they are called granulocytes or,
in clinical terminology, “polys,” because of
the multiple nuclei.
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The granulocytes and monocytes
protect the body against invading
organisms by ingesting them (i.e., by
phagocytosis) or by releasing
antimicrobial or inflammatory
substances that have multiple effects
that aid in destroying the offending
organism.
These cells are only formed in the
bone marrow.
These WBCs stored within the bone
marrow until they are needed in the
circulatory system.
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Neutrophiles and macrophages:
phagocytosis
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It is mainly the neutrophils and tissue
macrophages that attack and destroy invading
bacteria, viruses, and other injurious agents.
The neutrophils are mature cells that can attack
and destroy bacteria even in the circulating blood.
Neutrophil
Monocytes are immature cells while still in the
blood and have little ability to fight infectious
agents at that time. However, once they enter the
tissues, they mature into macrophages, and they
are extremely capable of combating disease agents
in the tissues.
Monocyte
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The most important function of the neutrophils and macrophages is
phagocytosis, which means cellular ingestion of the offending agent
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Eosinophils
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The eosinophils normally constitute about 2
percent of all the blood leukocytes.
Eosinophils are weak phagocytes, and they
exhibit chemotaxis; they do not seem to be
significant in protecting against the usual
types of infection.
Eosinophils, however, are often produced in
large numbers in people with parasitic
infections, and they migrate into tissues
diseased by parasites.
Eosinophils also have a special propensity to
collect in tissues in which allergic reactions
occur, such as in the peribronchial tissues of
the lungs in people with asthma and in the skin
after allergic skin reactions.
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Basophils and Mast Cells
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The basophils in the circulating blood are similar to the large tissue mast
cells located immediately outside many of the capillaries in the body.
Both mast cells and basophils liberate heparin into the blood.
The mast cells and basophils also release histamine, as well as smaller
quantities of bradykinin and serotonin. Indeed, it is mainly the mast
cells in inflamed tissues that release these substances during
inflammation.
The mast cells and basophils play an important role in some types of
allergic reactions. The type of antibody that causes allergic reactions,
the immunoglobulin E (IgE) interacts with mast cells and basophils. 11
Acquired Immunity
(Lymphocytes)
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Basic Types of Acquired Immunity:
Humoral and Cell Mediated
humoral immunity or B-cell immunity
The body (B lymphocytes) develops circulating antibodies, which
are globulin molecules in the blood plasma capable of attacking
the invading agent.
cell-mediated immunity or T-cell immunity
Large numbers of activated T lymphocytes that are specifically
crafted in the lymph nodes to destroy the foreign agent.
Both the antibodies and the activated lymphocytes are
formed in the lymphoid tissues of the body.
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