Abnormalities of White Blood Cells

White blood cell abnormalities are a significant area of study.
The objectives include contrasting reactive changes in granulocytes and lymph node morphology with neoplastic changes.
Leukocyte, platelet, and red blood cell production by hematopoietic stem cells and colony-forming units is a key process to understand.
Identifying the most common malignancies of lymphocyte precursors, more mature lymphocytes, and chronic leukemias is crucial.
Understanding the methods for identifying hematopoietic cells (cell surface antigens) is important.
The production of immunoglobulins and the development of multiple myeloma are also essential concepts.

Hematopoietic stem cells are the origin of all blood cells.
Multipotent progenitors give rise to multiple cell lineages.
Early progenitors have either lymphoid or myeloid potential.
Committed precursors then differentiate into specific cell types like neutrophils, monocytes, eosinophils, basophils, platelets, and erythrocytes.
Late precursors evolve into mature blood cell types.

Monoclonal antibodies target specific antigens on white blood cells for identification.
CD markers are important for classifying white blood cell types, like T-cells, B-cells, and precursor cells.
Different CD markers identify different stages and types of lymphocytes and other hematopoietic cells.
These markers are used in diagnosing blood cancers.

An elevated white blood cell count (leukocytosis) commonly results from inflammation or infection.
Granulocytes increase secondary to cytokines like TNF and IL-1.
Reduced margination and extravasation of granulocytes may happen with corticosteroids and catecholamines.
Lymphocytosis often arises from viral infections and tuberculosis.
Decreased white blood cell count (leukopenia) likely indicates autoimmune diseases, certain drugs, bone marrow issues, hereditary conditions, or ineffective erythropoiesis.
Severe infections or HIV can lower lymphocyte counts.

Lymph nodes have distinct zones, including primary and secondary lymphoid follicles, the paracortex, and the medulla.
Lymph node structure is crucial for lymphocytes proliferation and activation.
Afferent lymphatic vessels bring lymph to the node.
The lymphoid follicles contain mostly B cells and germinal centers.
The paracortex is rich in T cells.
Efferent lymphatic vessels carry lymph away.

Acute lymphadenitis involves B cell proliferation in germinal centers.
Chronic, non-specific lymphadenitis shows follicular hyperplasia without significant B-cell proliferation.

The World Health Organization classifies lymphoid neoplasms into precursor B-cell, peripheral B-cell, precursor T-cell and peripheral T-cell groups based on various factors and origin.
These neoplasms include leukemias and lymphomas.
Characterized by chromosomal aberrations, epigenetic modifications, and gene mutations that affect cell differentiation.
This classification system plays an important role in diagnosis.

Hematologic malignancies involve mutations in genes controlling cell differentiation, cell proliferation, and apoptosis.
These changes can lead to unregulated growth of hematopoietic cells, resulting in disorders like leukemia and lymphomas.
Genes like MCY and RAS are often implicated in proliferation abnormalities.

Acute lymphoblastic leukemias (ALL), a common childhood malignancy, commonly involves bleeding, infection, and CNS/liver/spleen involvement.
Chromosomal abnormalities and mutations in regulatory genes and transcription factors are often seen in ALL.
Chronic lymphocytic leukemias (CLL) are B-cell lymphomas associated with chromosomal abnormalities and frequently involve a gradual buildup of abnormal lymphocytes in lymph nodes, blood, and bone marrow.

Various subtypes of lymphomas, based on cell type and tissue involvement, like follicular, diffuse large B-cell, mantle-cell, Burkitt, and hairy-cell lymphomas are found.
These have distinguishing clinical presentations and cytological characteristics.

Hodgkin's lymphoma is characterized by the presence of Reed-Sternberg cells.
There are several subtypes of Hodgkin's lymphoma based on the morphology or types of cells that are present including:
- Nodular sclerosis
- Mixed cellularity
- Lymphocyte-predominance
- Lymphocyte-rich subtypes.

Multiple myeloma is a plasma cell cancer involving abnormal plasma cells that proliferate in bone marrow and form tumors throughout the body.
The disease affects the production and activation pathways for immunoglobulins and antibody production resulting in bone disease.

Immunoglobulin class and subclasses have different structures and roles in the immune system.
They include IgG, IgM, IgA, IgD, and IgE.
These have varying abilities to cross the placenta and activate complement.

Immunophenotyping techniques (using antibodies against specific antigens) allow for specific identification of lymphoid cell populations.
Used to determine the origin and characteristics of leukemias and lymphomas.

AML is characterized by chromosomal abnormalities, epigenetic modifications in differentiating genes, and impaired production of mature blood cells.
Myelodysplasia involve chromosomal defects, epigenetic factors (affecting gene expression), and impaired transcription factors resulting in ineffective erythropoiesis that disrupt the maturation process of blood cells.

Chronic myelogenous leukemia (CML) is associated with a specific chromosome translocation (BCR-ABL fusion protein).
The BCR-ABL fusion protein leads to continuous activation of an oncoprotein, and growth factors, further promoting uncontrollable cell proliferation and survival.

A plethora of other diseases and findings including specific cytological characterizations of the above are discussed in detail in various figures and tables.