This presentation gives you the detailed description of various cells & organs of immune systems that participates (particularly, in combination), make communication between themselves to regulate the whole immune system very precisely.

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Presented by: PRADDUM KUMAR NAMDEV
BSc (hons) ZOOLOGY
Enrollment NO. 17140007
IGNTU Amarkantak MP

2.  Cells of immune
system
◦ 1 Lymphocytes
 T-lymphocytes
 B-Lymphocytes
 NK cells
◦ 2. Phagocytic cells
 Monocytes
 Macrophages
◦ 3. granulocytes
 Neutrophils
 Basophils
 Eosinophils
 Mast cells
◦ 4. Dendriatic cells
 Organs of immune
system
◦ A. primary lymphoid organs
 Bone marrow
 Thymus
◦ B. secondary lymhoid organs:
 Lymph nodes
 Spleen
 MALT
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3.  WBCs are the principle cells of immune system
formed hematopoietic stem cell by the process of
hematopoiesis.
 Hematopoiesis occurs in yolk sac during 1st week of
gestation.
 After 3rd month of gestation, hematopoiesis occurs
in liver and spleen of fetus and after birth, it occurs
in bone marrow.
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4. 1. Lymphocytes
 T-lymphocytes
 B- lymphocytes
 NK cell
2. Phagocytic cells
 Monocytes
 Macrophages
3. Granulocytic cells
 Neutrophils
 Basophils
 Eosinophils
 Mast cells
4. Dendritic cells
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5. 
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6. 
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7.  Lymphocytes are small, round cells found in peripheral blood,
lymph, lymph nodes, lymphoid organs and in tissues.
 Lymphocytes represent 20-45% of total cells in peripheral blood
and 99% of total cells in lymph and lymph node.
 According to side lymphocytes are divided into small (5-8µm),
medium (8-12µm) and large (12-15µm).
 Depending on life span lymphocytes are classified into short lived
(2 weeks) and long lived (3 years or more or even lifelong).
 Broadly lymphocytes are divided into three sub-populations, on the
basis of function and cell membrane components.
◦ T-lymphocytes
◦ B-lymphocytes
◦ Natural killer cell
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8.  Monocytes and macrophages are mononuclear
phagocytic cells.
 Granulocyte-monocyte progenitor cell differentiates
into promonocytes and neutrophil.
 Promonocytes leaves the bone marrow and enter
into blood stream where they differentiate into
mature monocytes.
 Monocytes circulates in blood for about 8 hours,
during which they enlarges and then enter into
tissues and differentiates into specific macrophages
and dendritic cells.
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9.  Blood monocytes measure 12-15 µm with a single
lobed kidney shaped nucleus.
 It accounts for (2-8%) of blood leucocytes.
Immunological Functions of monocytes:
 Helps in antigen processing and presentation
 Releases cytokines
 Specialized function in tissues
 Cytotoxicity
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10.  Monocyte migrates to tissue and differentiates into macrophages.
 Differentiation of monocytes into macrophages involves following
changes:
 Cell enlarges 5-10 folds
 Intracellular granules increases in number and complexity
 Increase phagocytic ability
 Produces higher level of hydrolytic enzymes and cytokines
 Macrophages serve different functions in different tissues.
◦ Alveolar macrophages : in lungs
◦ Histiocyte: connective tissue
◦ Kuffer cell: liver
◦ Messangial cell: kidney
◦ Microglial cell: brain
◦ Osteoclast: bone
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11. Immunological functions of macrophages:
 Phagocytosis
 Antigen presentation to T-cell
 Secretion of lymphokines IL-1, IL-6. IL-12. TNF-α
etc. to activates inflammatory response
 Secretion of granulocyte monocyte colony (GMC)
stimulating factors.
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12. 1. NEUTROPHIL:
A. Neutrophils are (11-14µm) in diameter with multilobed
nucleus with granules in cytoplasm.
B. It constitutes 50-70 % of total circulating WBC and
remains for 7-8 hours in blood and then migrates to
tissues
C. Life span is 3-4 days.
D. Also known as polymorph nuclear (PMN) leucocyte.
E. Neutrophils is stained by both acidic and basic dye.
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13.  Phagocytic role in acute
inflammatory response.
 It is the first immune cell
to responds in
inflammation.
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14.  Eosinophil's are (11-15µm) in diameter, heavily
granulated with bilobed nucleus
 It is stained by acidic dye i.e. Eosin
 They are phagocytic and motile (migrate from cell
into tissue space).
 Comprise 2-5% of WBCs.
 Imp. Role in defense against protozoan and
helminth parasite by releasing cationic peptides &
reactive oxygen intermediates into extracellular
fluids.
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15.  Granules contain various hydrolytic enzymes that
kill parasites which are too large to be phagocytosed
by neutrophils.
 Provide allergic inflammation.
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16.  Basophils are non-phagocytic cell found in small
number in blood and tissue
 Cytoplasm contains large number of prominent
basophilic granules containing histamine, heparin,
serotonin, and other hydrolytic enzymes
 Stained by basic dyes
Immunological functions:
 Provide anaphylactic and atopic allergic reaction
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17.  Precursures are formed in bone marrow and
released into the blood in an undifferentiated state,
until they rach the tissues.
 They have ;large numbers of cytoplasmic granules
containing histamine.
 Mast cells and basophils play role in allergic
reactions.
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18.  Dendritic cells have long cytoplasmic externsions
that resembles to dendrites of nerve cell.
 They have highly pleomorphic with a small central
body and many long needle like processes.
 Dendritic cells are antigen presenting cell (APC)
because they possess MHC class.
Immunological functions:
 Involved in antigen presentation to T-cells during
primary immune response.
 Very little role in phagocytosis.
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20. Two main types of organs present in immune
system of humans:
1. Primary Lymphoid Organs
1. Bone marrow
2. Bursa of fabricius (in birds)
3. Thymus
2. Secondary Lymphoid Organs.
1. Lymph nodes
2. Spleen
3. Mucosa associated lymphoid tissue (MALT)
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22.  Primary lymphoid organs (PLO) are the major
sites of lymphocyte development i.e. lympho-
poiesis.
 Lymphocytes differentiate from lymphoid stem
cells, proliferate and mature into functional
cells called immuno-competent cells.
 In mammals, B-cell maturation occurs in the
bone marrow
 and T-cell maturation occurs in the thymus.
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23. A. location:
 It is found in the cavities of most bones in the body
including the skull, ribs, sternum, femur and spine.
 In birds, no bone marrow is found to be present,
instead a lymphoid organ named Bursa identified by
Fabricius called Bursa of Fabricius, is present and
performs the same duty of bone marrow of
mammals.
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24. 2. Structure
 Bone marrow of different bones mainly consists of a
sponge like reticular framework located between
long trabeculae.
 The spaces in this framework are filled with fat cells,
stromal fibroblasts and precursors of blood cells
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26. 3. Functions:
 The bone marrow is the main site of generation of all types of
circulating blood cells in adult and is the principal site of B-
cell maturation and proliferation.
 During foetal development, the generation of all blood cells,
called haematopoiesis, occurs initially in blood island of yolk
sac and para-aortic mesenchyme and later in the liver and
spleen.
 Gradually, these functions are shifted to bone marrow.
 All blood cells originate from haematopoietic stem cell and
become committed to differentiate along particular lineages
(erythroid, megakaryocyte granulocytic, monocyte and
lymphocytic).
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27.  Bone marrow is not only the source of all blood cells
but also provides the microenvironment for the
antigen independent differentiation of B-cell.
 Besides this, bone marrow serves as a secondary
lymphoid organ where mature, virgin, antigen
reactive lymphocytes (T & B cell) may respond to
antigen, trapped by antigen presenting cells, such as
macrophages.
 Thus, like spleen, bone marrow may provide an
antigen processing environment.
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28. I. location
 Thymus is located in the thoracic
cavity (in the mediastinum), just
above the heart and beneath the
breast bone.
 Location of the Thymus in the
Chest of Child.
II. Origin:
 In mammals thymus develops
from the endoderm of the third
and fourth pharyngeal pouch.
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29. III. Structure
 The thymus is flat, bilobed, greyish lympho-epithelial organ.
 Each lobe is made of lobules separated from each other by
strands of connective-tissue trabeculae and covered by a
capsule.
 Each lobule consists of two compartments the outer com-
partment (cortex) is densely packed with immature T-cells
(thymocytes)
 And, the inner compartment (medulla) is sparsely populated
with mature thymocytes which express CD44 (not found in the
cortical thymocytes).
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31.  There are basically four types of cells found in
thymus—
◦ Thymocytes
◦ dendritic cells
◦ epithelial cells
◦ Macrophages
 Both the cortex and medulla of the thymus are criss-
crossed by a three dimensional stromal-cell
network.
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32.  Out of four cell types, dendritic cells, epithelial cells and
macrophages act in a combine manner, as a framework to
assist in thymocyte maturation.
 Some thymic epithelial cells in the outer cortex, called nurse
cells, have long membrane processes which surround as
many as 50 thymocytes forming large multicellular
complexes.
 Other cortical epithelial cells have long inter-connecting
cytoplasmic processes that form a network.
 The thymocytes are differentiated and matured into different
types of T-cells under hormonal influence.
 Lymphoid progenitor cells formed in the bone marrow
migrate to the thymus under the influence of specialized
thymic environment.
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33.  Besides the primary lymphoid organs, there are some
other lymphoid organs which are referred to as
secondary lymphoid organs.
 Lymph nodes and spleen are the most important and
highly organized secondary lymphoid organs.
 Besides these, less organized lymphoid tissue
collectively called mucosal-associated lymphoid tissue
(MALT) which includes Peyer’s patches in the small
intestine, the tonsils, the appendix, as well as numerous
lymphoid follicles within the lamina propria of the
intestines and in the mucous membranes lining the
upper airways, bronchi and genital tract.
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35.  In case of closed blood vascular system, blood remain always
confined within the blood vessels.
 Lymph and lymphatic system bathe the tissue, tissue fluid
and cells.
 As because lymphatic system represents an accessory route
through which fluids or lymph can flow from interstitial
spaces into the blood, which is comprised by tiny lymphatic
vessels.
 There are different organized lymphoid tissues which are
located all along the lymphatic vessels, remain as diffuse
collections of lymphocytes and the macrophages and some
other are organized into structures called as the lymphoid
follicles.

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36.  These two remain as aggregates of various cells
surrounded by a network of draining lymphatic
capillaries.
 These are designated as secondary lymphoid tissues.
 The secondary lymphoid organs are rich in macrophages
and dendritic cells that trap and process antigens in T &
B lymphocytes, which mediate the immune responses.
 The anatomical structure of these organs is designed to
facilitate antigen trapping and its maximize
opportunities for processed antigen are to be presented
to antigen-sensitive cells.
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37. 1. Location:
 Lymph nodes are located at major junctions of the network of lymph flow through
lymphatic channels (lymphatic vessels.
2. structure:
 The lymph nodes of man are round or bean shaped structures placed on lymphatic
vessels so that they can filter out any foreign material carried in the lymph.
 Lymph nodes consist of a fibrous reticular network filled with lymphocytes,
macrophages and dendritic cells. Lymphatic sinuses penetrate the node.
 A sub-capsular sinus is located immediately under the connective tissue capsule of
the node; other sinuses pass through the node but are most prominent in a medulla.
 Afferent lymphatic vessels (those flowing into the node) enter the lymphatics node
around its circumference, and efferent lymphatic vessels (those flowing out of the
node) leave from depression (or hilus) on one side.
 The blood vessels supplying a lymph node also enter and leave via hilus.
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41.  The interior of a lymph node is divided into three
concentric zones—an outer cortex, a para-cortex and a
central medulla. Each of which provides a distinct micro-
environment.
 The cells in the cortex are predominantly (B-cells)
lymphocytes (arranged in nodules), macrophages and
follicular dendritic cells arranged in primary follicles.
 In lymph nodes, these follicles are stimulated by antigen,
turned into secondary follicles to expand upto germinal
centers where B-cells undergo somatic mutation.
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42.  Intense B-cell activation and differentiation into plasma and
memory B-cells.
 It occur in the germinal centers of lymph nodes.
 Cells that increase their ability to respond to an antigen leave the
germinal center to colonize other secondary lymphoid organs.
 Cells with reduced ability undergo apoptosis (programmed cell
death) and are removed by macrophages.
 The para-cortex sometime is referred to as thymus dependant area,
in contrast to the cortex, which is thymus independent area.
 The para-cortex is largely constituted with T-lymphocytes and
dendritic cells.
 The inter-digitating dendritic cells act as antigen presenting cells
(APCS) and thus express class II MHC (Major Histocompatibility
Complex) molecules.
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43.  The inner most layer of the lymph node is composed
of lymphocytes, forming inter connecting strands in
the medulla, called the medullary cord. Again these
medullary cords surround the medullary sinuses
which have plasma cells and some macrophages
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45. 1. Location
 Spleen, the secondary lymphoid organ is
located high in the left abdominal cavity.
 The spleen is specially adapted for filtering
blood and trapping blood-borne antigens and
respond to systemic infections.
2. Structure
 Spleen is one of the most important lymphoid
organ remain surrounded by a capsule.
 From the capsule, a no. of projections called
trabeculae remain extended to the interior to
form a compartmentalized structure.
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46.  There are two types of compartments, named red pulp and
white pulp.
 These two pulps are separated by a diffused marginal zone:
I. Red pulp:
 The red pulp of spleen consists of a network of sinusoids.
Sinusoids are with huge macrophages and erythrocytes.
Function:
 This splenic zone helps to destroy and remove old and
defective red blood cells.
 Some of the macrophages within the red pulp contain
engulfed red blood cells or iron pigments from degraded
hemoglobin.
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47. II. White pulp
 This zone is with T-lymphocytes. It surrounds the per arteriolar
lymphoid sheath (PALS).
Function:
 The T-cell-rich-PALS mediate the initial activation of B and T cells.
 Here, dendritic cells capture antigen and present it with T Helper
(TH) cells.
 In terms these activated T-cells activate B cells.
 Activated B and TH cells together migrate to primary follicles
present in the marginal zone.
 Primary follicles gradually develop characteristic secondary
follicles after antigenic challenge and rapidly give rise to B-cells and
plasma cells.
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49.  Besides lymph nodes, spleen, mucosal associated lymphoid tissue (MALT) is also
considered as secondary lymphoid organ.
I. Location:
 The majority of secondary lymphoid tissue in human body is located within the
lining of digestive, respiratory and genitourinary tracts.
 These are collectively called Mucosal Associated Lymphoid Tissue (MALT)
 There are several types of MALT.
 Two major MALT includes Bronchial Associated Lymphoid Tissue (BALT) and Gut
Associated Lymphoid Tissue (GALT)
 GALT includes the tonsils, adenoids, and specialised regions in the small intestine
called Peyer’s patches.
II. Structure:
 Loose cluster of lymphoid cells are present with little organizations in the lamina
propria of intestinal villi to organised structures such as the tonsils, appendix and
Peyer’s patches.
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50.  MALTs are meant for the production of huge
antibody-producing plasma cells which are very
essential for the body defense.
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51.  LIFE SCIENCES
FUNDAMENTALS AND PRACTICES –I
BY: PRANAV KUMAR AND USHA MINA
PUBLICATION: PATHFINDER, NEW DELHI
 WWW.BIOLOGYDISCUSSION.COM
 WWW.ONLINEBIOLOGYNOTES.COM
 IMAGE SOURCES
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 GOOGLE IMAGES
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