Makindo Medical Notes

Related Subjects: |Red blood cells |White blood cells |Lymphocytes |Platelets |Cryoprecipitate |Fresh Frozen Plasma |Blood Cell Maturation

White blood cells, or leukocytes, are a key component of the immune system, responsible for defending the body against infections and other foreign invaders. There are several types of white blood cells, each with distinct roles in the immune response. These cells are produced in the bone marrow and circulate in the bloodstream and lymphatic system.

Types of White Blood Cells

• Neutrophils
  • Mature neutrophils (12-15μm in diameter) have a segmented nucleus with 2-5 lobes.
  • Chromatin is dense and clumped, with lighter parachromatin areas.
  • Cytoplasm contains light-staining granules and a few azurophilic granules.
  • Primary role: first responders in the acute inflammatory process and phagocytosis of bacteria and fungi.
  • Normal range: 40-60% of total WBC count.
• Eosinophils
  • Characterized by large orange granules and are 12-15μm in diameter.
  • Nucleus usually has 2-3 lobes.
  • Granules contain Major Basic Protein (MBP), which is toxic to parasites such as helminths and schistosomiasis.
  • Normal range: 0-6% of total WBC count.
  • Primarily involved in allergic reactions and parasitic infections.
• Basophils
  • Basophils have purple-black, coarse granules and are 12-15μm in diameter.
  • The nucleus is segmented into 2-3 lobes.
  • Granules contain heparin and histamine, making them key players in hypersensitivity reactions.
  • Normal range: 0-1% of total WBC count.
• Monocytes
  • The largest cells in the peripheral blood, measuring 12-20μm in diameter.
  • Monocytes have a blue-grey cytoplasm and a kidney-shaped or lobulated nucleus.
  • They differentiate into macrophages once they enter tissues, playing an important role in chronic inflammation and phagocytosis.
  • Normal range: 0-10% of total WBC count.
• Lymphocytes
  • Lymphocytes vary greatly in size (7-20μm in diameter) and can be categorized into T cells, B cells, and natural killer (NK) cells.
  • Involved in the adaptive immune response, including antibody production and cellular immunity.
  • Normal range: 20-40% of total WBC count.

Causes of a Raised WBC Count (Leukocytosis)

• Acute or chronic myeloid leukaemia
• Acute lymphoblastic leukaemia
• Chronic lymphocytic leukaemia
• Lymphoma
• Myeloma
• Myelofibrosis
• Infection (bacterial, viral, fungal, or parasitic)
• Corticosteroid therapy
• Brisk gastrointestinal bleeding
• Stress, such as post-surgery
• Post-splenectomy

Causes of a Low WBC Count (Leukopenia)

• Bone marrow suppression (due to chemotherapy, radiation, or toxins)
• Aplastic anaemia
• Viral infections (e.g., HIV, hepatitis)
• Severe bacterial infections (sepsis)
• Autoimmune diseases (e.g., lupus)
• Nutritional deficiencies (e.g., vitamin B12 or folate)
• Steroid therapy

Subgroup-Specific Causes of Raised WBC Counts

• Neutrophilia (elevated neutrophils)
  • Bacterial infections
  • Inflammatory disorders (e.g., rheumatoid arthritis)
  • Stress, trauma, burns
  • Corticosteroid use
  • Chronic myeloid leukaemia (CML)
• Eosinophilia (elevated eosinophils)
  • Allergic reactions (e.g., asthma, hay fever)
  • Parasitic infections (e.g., helminths)
  • Autoimmune diseases (e.g., eosinophilic granulomatosis with polyangiitis)
  • Malignancies (e.g., Hodgkin's lymphoma)
• Basophilia (elevated basophils)
  • Chronic myeloid leukaemia (CML)
  • Allergic reactions (e.g., urticaria)
  • Hypothyroidism
  • Chronic inflammation (e.g., ulcerative colitis)
• Monocytosis (elevated monocytes)
  • Chronic infections (e.g., tuberculosis, syphilis)
  • Autoimmune diseases (e.g., lupus)
  • Chronic inflammation
  • Myelodysplastic syndromes
• Lymphocytosis (elevated lymphocytes)
  • Viral infections (e.g., Epstein-Barr virus, hepatitis)
  • Chronic lymphocytic leukaemia (CLL)
  • Lymphomas
  • Autoimmune diseases

Worrying Features Suggesting Malignancy

• Signs of sepsis or serious infection
• Ill patients with unexplained bleeding, bruising, or petechiae
• Enlarged liver, spleen, or lymph nodes
• Weight loss
• Abnormal blood film findings

References

• University of Virginia Teaching Site