Hematology and White Blood Cell Overview

White Blood Cells, Red Blood Cells, and Platelets

An overview of white blood cells, red blood cells, and platelets, including types and disorders.

White Blood Cells

White blood cells are fighters for infection and protect the body. Includes:

  • Bone marrow: the birthplace of all cells.
  • Innate immunity: the first line of defense, nonspecific, no memory (e.g., skin).
  • Adaptive immunity: B and T cells create blueprints, initiate with vaccines.

Once white blood cells cross into tissues, they become macrophages (phagocytes). Lymphocytes (T and B cells) provide longer immunity and a specific response. Granulocytes include neutrophils, eosinophils, and basophils.

Cell Development

Cells originate in the bone marrow from stem cells, which differentiate into white blood cells, red blood cells, and platelets. Blast cells are immature cells. T cells mature in the thymus, which shrinks with age, predisposing older adults to infections.

Lymphatic stem cells become B and T cells, while myeloid stem cells become red blood cells, platelets, and other white blood cell components.

Agranulocytes

Monocytes and lymphocytes lack granules. Monocytes become macrophages in tissues, performing phagocytosis and producing cytokines. Lymphocytes (T and B cells) offer long-term immunity. B cells produce antibodies.

Granulocytes

Neutrophils, eosinophils, and basophils contain granules. Eosinophils are associated with allergies and parasitic infections. Basophils activate with infection and inflammation, releasing histamine.

Neutrophils

Neutrophils are the first responders.

  • Mature neutrophils: segmented neutrophils (segs).
  • Immature neutrophils: bands.

In acute bacterial infections (e.g., pneumonia), the body uses mature neutrophils, leading to an increase in immature cells. This is a shift to the left, indicating more immature cells in circulation. This confirms that our neutrophils are being used up and we have a shift to the left which represents more immature cells in circulation.

Alterations in White Blood Cell Counts

  • Leukocytosis: excess of white blood cells (greater than 10,000 cells per microliter).
  • Leukopenia: deficiency of white blood cells (less than 5,000 per microliter).
  • Leukemoid reaction: counts above 50,000 per microliter.

Potential causes include blood loss, infections, spleen dysfunction, and organ necrosis.

Neutrophilia and Neutropenia

  • Neutrophilia: elevated neutrophil count, seen in bacterial infections, inflammation, and with smoking; drugs can also cause this.
  • Neutropenia: deficiency of neutrophils (less than 1,500 neutrophils per microliter), impairs the body's response to infection. Reverse isolation (neutropenic precautions) protects patients with neutropenia from external pathogens due to patients not being able to mount response.

Lymphocyte Abnormalities

Abnormal lymphocyte counts increase the risk of infections and opportunistic infections.

Risk Factors

  • Genetic mutations.
  • Environmental exposures.

Symptoms

  • Tiredness.
  • Thrombocytopenia (bruising and bleeding).
  • Bone pain.
  • Enlarged lymph nodes.

Diagnosis

  • Blood counts.
  • Bone marrow aspirations.

Treatments

  • Chemotherapy.
  • Radiation.

Chronic Lymphocytic Leukemia Characteristics

  • Older individuals, over 70, typically male.
  • Caused by DNA disruption or environmental hazards (coal mine workers, farmers, pesticides).
  • Targets nonfunctional B cells, impairing antibody production.

Acute Myelogenous Leukemia

  • Quick onset, earlier in life.
  • Can invade other tissues (skin, lungs, spleen, liver).
  • Prior chemotherapy exposure can elevate risk.

Lymphatic System and Lymphomas

Lymphoma spread easily due to the vast lymphatic system.

Hodgkin's Lymphoma

Diagnosed by the presence of Reed-Sternberg cells (owl eyes).

Non-Hodgkin's Lymphoma:

Can include B cells plus other lymphatic fibers like T cells and natural killer cells. Can be aggressive in young children due to highly vascularized and developing bone marrow.

Non-Hodgkin's Lymphoma Causes:

  • Chromosomal changes.
  • Pathogens (HIV).
  • Immunosuppressive therapy.
  • Environmental exposures.

Enlarged, painless lymph node is a common sign.

Hodgkin's Lymphoma:

Involves only B cells and can occur in young adults and adolescents.