Granulocytes
Monocytes, and
reticuloendothelial system
Fundamental Functions of white
blood cells
• Defense against invading micro-organisms.
• Recognition and destruction of neoplastic
cells.
• Clearing of senescent (old) and apoptotic cells
by phagocytosis.
• Production of various cytokines
White blood cells (WBC’s)
• Divided into 2 main groups:
• 1) PHAGOCYTES: include neutrophils, eosinophils,
basophils, and
• monocytes.
• 2) Immunocytes: include lymphocytes and plasma cells.
• - Neutrophils, eosinophils, basophils are called
granulocytes because they contain granules in their
cytoplasm.
- Production of WBC occurs in BM.
- Only mature phagocytes and lymphocytes are found in
blood.
Neutrophil
• Granulopoiesis is the production of
granulocytes in BM.
• Many growth factors are involved in
granulopoiesis including IL1, IL3, IL5, GMCSF,
• AND G-CSF.
• Neutrophils are released from BM to blood
and spend only 6-10 h in the circulation before
they move into body tissues.
Neutrophil
• - The earliest recognizable granulocyte
precursors in the marrow are promyelocytes.
- In the tissues, they function as phagocytic cells.
- Neutophil live in tissues about 4-5 days.
- Eosinophils and basophils are produced in the
marrow in a similar process.
Neutrophil
• Structure:
- This cell has a large nucleus consisting of 2-5
lobes and a pale cytoplasm.
- The cytoplasm contains many pink-blue or grey
granules.
- Granules can be primary or secondary granules.
- Granules contain lysosomal enzymes which are
important for phagocytosis (ingestion and killing) of
bacteria or old cells.
• Primacy granules contains myeloperoxidase
and acid phosphatase
• Secondary granules contain collagenase,
lactoferrin and lysozymes
• Count: Neutrophils are the most numerous
leucocytes comprising 65% of circulating
phagocytes
• Function: Killing of bacteria and fungi.
Eosinophils
• Structure:
Similar to neutrophil structure except:
1- granules in the cytoplasm are courser.
2- granules are bright orange to deep red.
3- maximum number of nuclear lobes is 3.
• Count: (5-10 % of WBC).
• Function:
1- Involved in allergic reactions.
2- Defense against parasites.
• Cytokines control: IL-5 is the most lineage-specific
factor involved in eosinophil production.
Basophils
• Structure:
• - Basophils have a bilobed nucleus.
• - Have many dark granules which cover the
nucleus.
- Granules contain heparin and histamine.
• They express on their surface the FC receptor
that binds to the Fc portion of IgE antibody.
- When they move from blood to tissue they
become mast cells.
Basophils
• - Count: occasional in peripheral blood (less
than 0.5 % in blood WBC).
• - Functions:
• 1-have significant roles in a number of allergic
and inflammatory disorders.
• 2- host defense mechanisms against parasites.
• - Cytokines: The major growth and
differentiation factor for basophils is IL-3.
Monocytes
• Monocytes production occurs in the bone
marrow and is controlled by growth factors.
• Structure:
-Larger than other WBC.
-Have large central oval nucleus with clumped
chromatin.
-Blue cytoplasm that contain fine vacuoles.
- May have cytoplasmic granules.
• Production and maturation:
- Once produced in BM, they live in blood for
20-40 h, before they enter the tissues.
- In the tissue they mature become
macrophages and live for months-years.
- Cytokines: GM-CSF and M-CSF are involved in
production and activation.
Phagocytosis
• Phagocytes ingest and destroy pathogens and
cell debris.
• Phagocytes are attracted to bacteria at the
site of inflammation by chemotactic
substances released from damaged tissues or
by complement components.
Phagocytosis
• Opsonization is the coating of cells or foreign
particles by immunoglobulin or complement;
this aids phagocytosis (engulfment) because
phagocytes have Fc and C3b receptors.
• Killing involves reduction of pH within the
phagocytic vacuole, the release of granule
contents and the production of antimicrobial
oxidants and superoxides.