Chapter 15. White Blood Cell Disorders. White Blood Cell Disorders.
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In Chapter 15, you will be introduced to the various disorders of leukocytes. Included in this chapter will be a discussion on the kinetics and functions of neutrophils, disorders of neutrophils, and other morphologic changes of neutrophils. The function and morphology of lymphocytes will also be covered. Diseases that affect lymphocytes are discussed.
Once in the circulatory system, the neutrophils divide up into two pools:
Marginating pool: These neutrophils remain in the circulatory system searching for an area of inflammation. When inflammation is found, these neutrophils leave the circulatory system by process of diapedesis and enter surrounding tissues.
Circulating pool: Leave the blood stream by random migration and do not return to the bloodstream.
Neutrophils are believed to survive 2-5 days after entering the tissues.
Variations in the numbers of neutrophils is a useful diagnostic tool; Variations reflect response of neutrophils to underlying disease (i.e. bacterial infection) or of another disorder such as leukemia.
Neutrophils play central role in fighting infections and inflammatory agents. Can reach area of inflammation within minutes by migrating (diapedesis) from circulatory system to site of infection.
Neutrophilia is increase in relative number of neutrophils in response to infection or inflammatory process. Accelerated release from bone marrow seen as "shift to left" which is defined as increased number of metamyelocytes and bands in peripheral blood. Rarely see more immature neutrophil forms in infections (will see more immature forms in leukemia).
In addition to changes in neutrophil number, will see morphologic changes such as toxic granulation, Dohle bodies, and cytoplasmic vacuoles:
Toxic granulation: granules become larger and stain more darkly. Granules tend to be primary granules that are peroxidase positive. Frequently seen in severe infections.
Dohle bodies: pale blue cytoplasmic inclusions. Seen on periphery of cell. Consist of few strands of rough endoplasmic reticulum that have banded together.
Vacuoles: Neutrophils may develop vacuoles in cytoplasm. May see ingested microorganisms as well.
Presence of any of these changes may suggest progression toward sepsis; however, are not specifically related to infections. May see in massive trauma, during pregnancy, in inflammatory responses, and in drug reactions.
In the leukocyte, there are pH changes, dumping of digestive enzymes into the phagolysosome, production of hydrogen peroxide and superoxides. These digestion processes are collectively called respiratory burst. These oxygen metabolites injure the organism and interact with other granular contents to produce toxic agents such as hydrochloric acid (household bleach).
Features include recurrent bacterial infections, partial albinism, and presence of giant lysosomal granules in cells such as granulocytes, monocytes, lymphocytes, and platelets. Mild bleeding tendencies may occur.
Have progressive neurologic complications during childhood. Many patients die as result of infection during childhood. Adults enter into accelerated phase that progresses through pancytopenia, organomegaly, systemic infections, and eventually, death. Staphylococcus aureus primary cause of infections.
**Have inefficient and prolonged bacterial killing. Release of lysosomal enzymes impaired by abnormal granules. In Wright's stain, giant granules more likely seen in lymphocytes (stain deep purple to dark red).
Management includes prophylactic antibiotic treatment and high daily doses of ascorbic acid. In cases of infection, aggressive intravenous treatment required.
Bone marrow transplant only hope of cure. Should be performed before accelerated phase begins.
May be inherited as either sex-linked-recessive or as autosomal-recessive. Regardless of form, end result is that superoxide can not be produced, and in turn, bacterial killing is ineffective. Ingestion of bacteria, degranulation, and phagolysosome formation normal.
Diagnosis made by demonstrating bactericidal defect resulting from absence of respiratory burst on nitroblue tetrazolium test (NTB), or by measuring respiratory burst activity by flow cytometry.
Aggressive prophylactic antibiotic therapy begun as soon as diagnosis made. Gamma interferon effective in limiting frequency of infections. Granulocyte transfusions useful. Bone marrow transplants beneficial in children.
Nucleus is bilobed or lacks lobes altogether. Nuclear chromatin excessively coarse and condensed. Nuclei described as "dumbbell" or "pince-nez" appearing with two symmetric lobes being joined by filament.
True Pelger-Huet is autosomal-dominant condition. Is benign condition.
Presence of prominent, dark staining, coarse granules in many or all cell lines. Prominent granules are similar to toxic granulation, except they are larger and permanent (not a transient change cause by infection or toxins).
Demonstrates larger, blue-staining cytoplasm in the granulocytes, resembling Dohle bodies.
Can trace course of disease by testing for IgM and IgG antibodies. IgM antibodies formed early in infection, while IgG antibodies formed after a couple of weeks. Periodic testing of antibody titers can trace course of disease through acute and convalescent phases.
If malignancies suspected, lymphocytes may be distinguished by immunophenotyping tests.