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Leukopoiesis Normal and abnormal. Barrett W. Dick, M.D. Director, Hematology Laboratories Memorial Medical Center Springfield. IL Clinical Professor, Pathology and Medicine Southern Illinois School of Medicine June, 2000. Evolution of White Cells. Stem cell vs. Progenitor Cell.
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LeukopoiesisNormal and abnormal Barrett W. Dick, M.D. Director, Hematology Laboratories Memorial Medical Center Springfield. IL Clinical Professor, Pathology and Medicine Southern Illinois School of Medicine June, 2000
Stem cell vs. Progenitor Cell • Stem cell: a primitive cell that is capable of both self renewal and differentiation. Upon differentiation, it can develop into myeloid or lymphoid lineages. • Progenitor cell: a primitive cell beyond the stem cell stage that is committed to lineage differentiation
Evidence for Separate Common Progenitor Cell for B Lymphocytes and Myeloid Progenitor • Philadelphia chromosome is found in CML and a significant fraction of ALL, common B cell type. • Blast crisis in CML is frequently lymphoblastic, almost always B cell type.
Neutrophil segmented form - "seg" To be considered a segmented form, there must be at least one point where the the nucleus is segmented into two lobes with the connection between the containing no visible DNA (1). If there is visible DNA (2), it is not considered a segment.
Neutrophil Maturation When a differential count is performed, traditionally, the device used for tallying the cells is arranged with the least mature cells on the left. This is the historic origin of the term "shift to the left" describing a relative increase in immature forms.
Transformed lymphocytes aka:"Reactive", "Large", "Variant" or "Atypical"
Smear Examination Thin Area Feather Edge
Performance of a White Cell Differential - General Principles • Scan at low power: • Identify appropriate thin area • Evaluate quality of smear • High power oil- 50X or 100X: • Scan for abnormal cells and make a qualitative assessment • Perform 200 cell differential • Rescan to confirm that differential is an accurate representation
Confidence Interval for Manual Differentials • On a 1-200 cell manual differential, if a cell type is reported as: • "50%", the 95% C.I. is ~40% - 60% . • ‘1%’, the C.I. is ~0-8% . • A statistically meaningful differential - 1000 cell differential required but not practical • Conclusions: • Scanning the smear for abnormalities is more important than the diff • Absolute counts from the machine are more accurate
Exceptions to the Absolute Counts "Rule" • % Segs compared % Bands - Ratio of the two defines a "left shift" • % Mono’s - Relative monocytosis is important in some clinical situations • Agranuloctosis/neutropenia- Monocytosis frequently predicts bone marrow recovery • Relative or absolute monocytosis is a frequent finding in myelodysplastic syndromes
Wbc Normal Ranges (cells/cumm) • Neutrophils: 1500-6500 (Caucasians) • 800-1200 (African subpopulation • Lymphocytes: 1500-3000 • Monocytes: <1000 • Eosinophils: <700 • Basophils: <200 • Seg/Band Ratio: 5-6:1 • Relative Monocytes: <10%
Principles of Blood Smear Examination • A 200 cell differential is a semi-quantitative estimate of the actual diff because the sampling error is very high - you are looking at a very small sample of a very large population • When a differential is reported, what it should mean is that an experienced individual has examined that smear and, other than what was reported, no significant abnormalities were seen • In practice, because of forced cutbacks in staffing, this currently is unlikely to be the case in most institutions • Conclusion: You better learn to examine blood smears
Basophil Basophil granules are very soluble. In this example they are partially dissolved and are easily mistaken for toxic granules in a neutrophil. The background cytoplasm in a basophil is gray in contrast to the salmon-pink color in a neutrophil
Large Transformed Lymphocyte In a normal blood smear, 15-17% of the lymphocytes may be large lymphocytes.
Large Granular Lymphocyte Frequently, but arbitrarily included as reactive lymphocytes. The granules identify them as "killer" cells.,
Large granular lymphocytes- "LGL’s" • There are at least two distinct subclasses of killer cells • ADCC: antibody dependent cytotoxic cells; a subclass of CD8 cells. Require the presence of an antibody to be functional • Natural killer cells: do not require the presence of an antibody
Neutrophil with Dohle Body Dohle Bodies are condensations of cytoplasmic RNA, stain blue-gray, and have the same significance as toxic granulation.
Hypersegmented Neutrophil Hypersegmented neutrophils are classically associated with megaloblastic processes. However, they are commonly present when there is a neutrophilia. Rarely, it is a hereditary abnormality.
Transformed lymphocytes aka:"Reactive", "Large", "Variant" or "Atypical"
Lymphoblasts, Acute Lymphocytic Leukemia Lymphoblasts are usually smaller than myeloblasts and frequently have little or no visible cytoplasm.
Myelocyte - Eo/Baso? Abnormal myelocyte frequently interpreted as having both eosinophil and basophil granules. Most likely this is a normal eosinophil myelocyte with primary granules. In either case the significance is they are virtually only seen in the blood in chronic myeloproliferativedisorders.
Pelger-Huet Anomaly The Pelger-Huet anomaly can be either hereditary or acquired. The main features are exaggerated nuclear clumping and hyposegmetation. The latter manifests itself as "increased " band counts.
Pseudo Pelger-Huet Anomaly Cells that look metamyelocytes are almost never found in the hereditary form.