Leukocytes

Introduction to Leukocytes

• Leukocytes, commonly known as white blood cells (WBCs), are crucial components of the immune system.

• They are produced in red bone marrow.

Major Groups of Leukocytes

• Leukocytes are primarily categorized into two main groups:

  • Granular Leukocytes

  • These leukocytes have visibly identifiable granules in their cytoplasm when observed under a microscope.

  • Granules are tiny sacs containing essential chemicals for immune responses.

  • Three types of granular leukocytes include:

    1. Neutrophils

    2. Basophils

    3. Eosinophils

    • Each of these plays a distinct role in combating pathogens and microorganisms.

      • Neutrophils are typically the first responders to microbial invasion in tissues. When microbes enter the body, neutrophils are the first leukocytes to migrate to the affected area.

  • Agranular Leukocytes

  • These cells also have granules; however, the granules are not easily visible under the microscope.

  • The two main groups of agranulocytes are:

    1. Monocytes

    2. Lymphocytes

Lymphocytes

• Lymphocytes, a subgroup of agranular leukocytes, further divide into three categories:

  1. T Lymphocytes (T cells)

  2. B Lymphocytes (B cells)

  3. Natural Killer (NK) Cells

• These lymphocytes are proficient in targeting and killing infected or cancerous cells.

Function of B Lymphocytes

• When activated, B lymphocytes can differentiate into plasma cells, which are specifically responsible for the release of immunoglobulin antibodies.

  • Plasma cells (also known as plasmacytes) are the active forms of B lymphocytes that produce antibodies essential for immune defense.

  • It is important to note that plasma cells are categorized as agranular because they do not have visible granules.

Role of Monocytes and Macrophages

• Monocytes are capable of migrating from the bloodstream into tissues, where they differentiate into macrophages.

• Macrophages are specialized cells that excel in phagocytosis, the process of engulfing and digesting solid particles, including pathogens.

Major Phagocytes in the Immune System

• In summary, two primary types of phagocytes in the immune system are:

  1. Neutrophils: These are granular leukocytes and the first to respond to an infection.

  2. Macrophages: Derived from monocytes, they represent another class of crucial phagocytes in the immune response.

• To reiterate, macrophages originate from differentiated monocytes and, like lymphocytes, are also agranular.