PATHOLOGY PRACTICAL # 8 Total Leukocyte Count (TLC) and its interpretation

Total Leukocyte Count (TLC) and its interpretation:

Leukocytes include neutrophils, eosinophils, and basophils, monocytes and lymphocytes.

Granulocytes only include neutrophils, eosinophils, and basophils. While other cells are called agranulocytes such as lymphocytes, monocytes etc.. Neutrophils are the most efficient at phagocytosis and are the principal cells of innate immune defense against bacteria and fungi. 

TLC is recommended to evaluate White cell counting for diagnosing bacterial and viral infections, toxic metabolic processes, diagnosing leukemia stages etc.

                     Normal Adult Total 3500-10,000 cells/cc

CELL TYPE	RANGE (AVG)
Neutrophil	2000-7000 (3700)
Lymphocytes	1500-4000 (2500)
Monocytes	200-1000 (400)
Eosinophils	0-700 (150)
Basophils	0-150 (30)

CLINICAL UTILITY OF CELL COUNTS

CLINICAL CONDITION	DIFFERENTIAL COUNT FINDING
acute infection	granulocytosis
chronic inflammation	monocytosis
parasitic infection	eosinophilia
viral infection	lymphocytosis
aplastic anemia	neutropenia
acute leukemia	immature cells or blasts

Marked Leukocytosis can be due to benign or malignant causes:

Peripheral Blood Findings	(non-malignant)	Chronic Myelogenous Leukemia
WBC > 100000	rare	often
Basophilia	rare	often
Chromosomal abnormalities	never	always
Splenomegaly	rare	often

 



Eosinophils

Special function of eosinophils is to fight helminths, ticks, and parasites.

Eosinophils can also suppress or enhance hypersensitivity by mobilizing or destroying histamine.

Eosinophils have many red granules.

Eosinophilia is almost always caused by allergic reactions or parasitic infections.  It can cause       tissue destruction.

Basophils

Basophils release histamine and heparin.

They are full of large purple granules.

Basophilia is associated with acute allergic reactions like food allergies.

Monocytes

Monocytes are important for phagocytosis They are also involved in clearing apoptotic cells.

Monocytosis is caused by chronic infection or an inflammatory disease.

Lymphocytes

There are several kinds of lymphocytes (although they all look alike under the microscope), each with different functions to perform . The most common types of lymphocytes are

• B lymphocytes ("B cells"). These are responsible for making antibodies.
• T lymphocytes ("T cells"). There are several subsets of these:
  • inflammatory T cells that recruit macrophages and neutrophils to the site of infection or other tissue damage
  • cytotoxic T lymphocytes (CTLs) that kill virus-infected and, perhaps, tumor cells
  • helper T cells that enhance the production of antibodies by activating B cells

Although bone marrow is the ultimate source of lymphocytes, the lymphocytes that will become T cells migrate from the bone marrow to the thymus. where they mature. Both B cells and T cells also take up residence in lymph nodes, the spleen and other tissues where they

• encounter antigens;
• continue to divide by mitosis;
• mature into fully functional cells.

Common Causes of Altered Leukocyte Counts
	Decreased	Increased
Neutrophil	Congenital Hereditary neutropenia Acquired Bone marrow disease Immune reactions Drugs Gram-negative septicemia	Acquired Infections Tissue destruction Corticosteroids, lithium Neoplastic growth Leukemoid reaction, pregnancy, smoking
Lymphocyte	Congenital Congenital immunodeficiency disease Acquired Severe infection Drugs (Corticosteroids, alkylating) GI disease Immunodeficiency	Acquired Viral infection (EBV, hepatitis, etc.) Some fungal, parasitic infections Rare bacterial infection (Pertussis) Allergic reactions/drug sensitivities, smoking, CLL Immunologic disease
Monocyte	Acquired Hairy cell leukemia Corticosteroids	Acquired Mycobacterial infection Tuberculosis, syphilis Subacute bacterial endocarditis Inflammatory responses Myeloproliferative disorders
Eosinophil	Acquired Bacterial infection ACTH administration	Acquired Parasitic infections, Asthma, Hypersensitivity reactions Pulmonary disease Myeloproliferative diseases
Basophil	Acquired Corticosteroids	Acquired Myeloproliferative syndromes Lymphoproliferative disease Hypersensitivity reactions Hodgkin’s disease Some viral infections Myxedema