THE INFLAMMATORY CELLS
Tne cells participating in acute and chronic inflammation arce circulating leucocytes, plasma cells and tissue
macrophages.
1.Polymorphonuclear Neutrophils (PMNs)
Commonly calledas neutrophils or polymorphs, these cells along with basophils and eosinophils are known
as granulocytes due to the presence of granules in the cytoplasm. T
hese granules contain many substances like proteases, myeloperoxidase, lysozyme, esterase, aryl sulfatase,
acid and alkaline phosphatase, and cationic proteins.
" The diameter of neutrophils ranges from 10 to I5 um and are actively motile. These cells comprise 40-75%
of circulating leucocytes and their number is increased in blood (neutrophilia) and tissues in acute bacterial
infections. These cells arise in the bone marrow from stem cells The functions of neutrophils in
inflammation are as follows:
i) Initial phagocytosis of microorganisms as they form the first line of body defense in bacterial infection.
The steps involved are adhesion of neutrophils to vascular endothelium, emigrationthrough the vessel wall,
chemotaxis, engulfinent, degranulation, killing anddegradation of the foreign material.
ii) Engulfment of antigen-antibody complexes and nonmicrobial material.
destruction of the glomeruli and small blood
ii) Harmful effect of neutrophils in causing basement membrane
vessels.
2. Eosinophils
These are larger than neutrophils but are fewer in number, comprising 1 to 69% of total blood
leucocytes.
Eosinophils share many structural and functional similarities with neutrophils like their production in
the bone marrow, locomotion, phagocytosis, lobed nucleus and presence of granules in the cytoplasm
containing a variety of enzymes, of which major basic protein and eosinophil cationic protein are the
most important which have bactericidal and toxic action against helminthic parasites.
Granules of eosinophils are richer in myeloperoxidase than neutrophills and lack lys0zyme.
High level of steroid hormones leads to fall in number of eosinophils and even disappearance from
blood. The absolute number of eosinophils is increased in the following conditions and, thus, they
partake in inflammatory responses associated with these conditions:
i)allergic conditions;
i)parasitic infestations;
iii) skindiseases; and
iv) certain malignant lymphomas.
3. Basophils (Mast Cells)
The basophils comprise about 1% oftissue.T
circulating leucocytes and are morphologically and
pharmacologically similar to mast cells of
hese cells contain coarse basophilic granules in the cytoplasm and a polymorphonuclear nucleus. These
granules are laden with heparin and histamine.
Basophils and mast cells have receptors for IgE and degranulate when cross-linked with antigen. The
role of these cells in inflammation are:
i)In immediate and delayed type of hypersensitivity reactions; and
ii)Release of histamine by IgE-sensitised basophils.
4. Lymphocytes
Next to neutrophils, these cells are the most numerous of the circulating leucocytes (20-45%).
Apart from blood, lymphocytes are present in large numbers in spleen, thymus, Iymph nodes and
mucosa-associated lymphoid tissue (MALT).
They have scanty cytoplasm and consist almost entirely of nucleus. In addition these cells participate
inthe following types of inflammatory responses:
Tne cells participating in acute and chronic inflammation arce circulating leucocytes, plasma cells and tissue
macrophages.
1.Polymorphonuclear Neutrophils (PMNs)
Commonly calledas neutrophils or polymorphs, these cells along with basophils and eosinophils are known
as granulocytes due to the presence of granules in the cytoplasm. T
hese granules contain many substances like proteases, myeloperoxidase, lysozyme, esterase, aryl sulfatase,
acid and alkaline phosphatase, and cationic proteins.
" The diameter of neutrophils ranges from 10 to I5 um and are actively motile. These cells comprise 40-75%
of circulating leucocytes and their number is increased in blood (neutrophilia) and tissues in acute bacterial
infections. These cells arise in the bone marrow from stem cells The functions of neutrophils in
inflammation are as follows:
i) Initial phagocytosis of microorganisms as they form the first line of body defense in bacterial infection.
The steps involved are adhesion of neutrophils to vascular endothelium, emigrationthrough the vessel wall,
chemotaxis, engulfinent, degranulation, killing anddegradation of the foreign material.
ii) Engulfment of antigen-antibody complexes and nonmicrobial material.
destruction of the glomeruli and small blood
ii) Harmful effect of neutrophils in causing basement membrane
vessels.
2. Eosinophils
These are larger than neutrophils but are fewer in number, comprising 1 to 69% of total blood
leucocytes.
Eosinophils share many structural and functional similarities with neutrophils like their production in
the bone marrow, locomotion, phagocytosis, lobed nucleus and presence of granules in the cytoplasm
containing a variety of enzymes, of which major basic protein and eosinophil cationic protein are the
most important which have bactericidal and toxic action against helminthic parasites.
Granules of eosinophils are richer in myeloperoxidase than neutrophills and lack lys0zyme.
High level of steroid hormones leads to fall in number of eosinophils and even disappearance from
blood. The absolute number of eosinophils is increased in the following conditions and, thus, they
partake in inflammatory responses associated with these conditions:
i)allergic conditions;
i)parasitic infestations;
iii) skindiseases; and
iv) certain malignant lymphomas.
3. Basophils (Mast Cells)
The basophils comprise about 1% oftissue.T
circulating leucocytes and are morphologically and
pharmacologically similar to mast cells of
hese cells contain coarse basophilic granules in the cytoplasm and a polymorphonuclear nucleus. These
granules are laden with heparin and histamine.
Basophils and mast cells have receptors for IgE and degranulate when cross-linked with antigen. The
role of these cells in inflammation are:
i)In immediate and delayed type of hypersensitivity reactions; and
ii)Release of histamine by IgE-sensitised basophils.
4. Lymphocytes
Next to neutrophils, these cells are the most numerous of the circulating leucocytes (20-45%).
Apart from blood, lymphocytes are present in large numbers in spleen, thymus, Iymph nodes and
mucosa-associated lymphoid tissue (MALT).
They have scanty cytoplasm and consist almost entirely of nucleus. In addition these cells participate
inthe following types of inflammatory responses:
