Clinical Immunology and
serology Practice
MLIS-201
Prof. Dr. Ezzat M Hassan
Immunology Dept.,
Med. Res. Inst., Alex. Univ.
Outcomes
By the end of the lecture the students will be able to
• Recognize Structure of the immune system.
• Enumerate the Cell Frequency of Different Leukocytes
in Blood of Healthy Individuals
Structure of
the immune system
Immune system
Cells
Organs
1-Cells of
the Immune System
Cells of the Immune System
Myeloid cells
lymphoid cells
Granulocytic
Monocytic
T-cells
B-cells
Neutrophils
Basophils
Eosinophils
Macrophages
Langerhans &
Kupffer cells
Dendritic cells?
Helper
Cytotoxic
Suppressor
Plasma
cells
Dendritic
cells?
Cell Frequency of Different Leukocytes in
Blood of Healthy Individuals
~ 60% neutrophils (50% - 70%)
~ 3% eosinophils (>0% - 5%)
~ 0.5% basophils (>0% - 2%)
~ 5% monocytes (1% - 9%)
~ 30% lymphocytes (20% - 40%)
Myeloid Lineage
 Granulocytes
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Neutrophils
Eosinophils
Basophils
 Monocytes
Macrophages
 Megakaryocytes
Platelets
 Erythrocytes (RBC)
 Dendritic cells (APC)
Neutrophils
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60-70% of WBCs
Multi-lobed nucleus
Granulated cytoplasm
Life span is 2-3days
Prominent in inflammatory response
Leukocytosis is marker for infectious process
Dead neutrophils make up a large proportion of pus.
Actively phagocytic
Eosinophils
 ~2% of WBCs
 Bi-lobed nucleus
 Granulated cytoplasm
 Stains red with acid dye (eosin)
 Prominent in response to parasitic infections
 Phagocytic
Basophils
 <1% of WBCs
 Lobed nucleus
 Heavily granulated cytoplasm
 Stains blue with basic dye
 Prominent in allergic responses
 Non-phagocytic
 Secrete allergic & inflammatory mediators
Monocytes and Macrophages
Monocytes:
 Large WBCs
 Monocytes are circulating precursors of Macrophages.
Macrophages
 Found in the organs, not the blood.
 Made in bone marrow as monocytes
 Called macrophages once they reach organs.
 Long lived
 Phagocytic
 Initiate immune responses as they display antigens to the
lymphocytes (APC).
 Activated by cytokines and gamma interferon
 Secretes numerous immune response factors
Phagocytosis
Macrophages
Bifunctional
Antigen
presentation
Liver
Skin
Kuppfer cells
CNS
Spleen,lung
Denteritic cells
Microglia
Macrophages
Mast Cells
 Found in many different tissues
 Contains granules which release histamine
 Play role in allergic reactions
Dendritic Cells
 Have long “dendrites”
 Major role as APC
 Stimulated by innate response
 Have constitutive MHC II expression
 Phagocytic
APC
T cell
APC INTERACTING WITH T CELL
Lymphoid Lineage
Lymphoid cells
NK (Natural killer cells)
T-cells
B-cells
Lymphocyte Production
 Lymphocytes are produced in:
 lymphoid tissues (e.g., tonsils)
 lymphoid organs (e.g., spleen, thymus)
 Bone marrow
 Make up 20–30% of circulating leukocytes
 Majority are stored in lymphoid organs, not circulating
(remember that only about 1% of your WBCs are in the
blood)
Classes of
Circulating Lymphocytes
 T cells: thymus-dependent
 Make up 80% of circulating lymphocytes
 B cells: bone–marrow derived
 Make up 10–15% of circulating lymphocytes
 NK cells: natural killer cells
 Make up 5–10% of circulating lymphocytes
Lymphocytes
1-T Lymphocytes

Mature in thymus
Have T cell receptors (TCRs)
Recognize Ag on cells only

CELL-MEDIATED IMMUNE RESPONSE
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T cell subclasses:
1.
Cytotoxic T cells

Helper T cells
2.
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Stimulate function of T cells and B cells
Suppressor T cells
3.
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Inhibit function of T cells and B cells
Regulatory T cells
4.
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5.
Attack cells infected by viruses & malignant cells
Regulate the functions other T cells
Memomry T cells
For secondary immune responses
Lymphocytes
2-B Lymphocytes
 Mature in bone marrow
 Have membrane-bound Ab(~10,000 per cell)
 Go from “naive” to activated.
 Differentiate into plasma cells, which produce and
secrete antibodies (immunoglobins)
 HUMORAL IMMUNE RESPONSE
 Plasma cells are Ab secretors

~1-2 week life span
B- cells
Plasma cells
Immunoglobulins
B-memory
-Long lived
-2ry immune response
B cells
Natural Killer (NK) Cells
 Also called large granular lymphocytes
 Responsible for immunological surveillance
 Lack T and B cell markers
 Lack Ag receptors
 Involved with Ab-dependent cell-mediated
cytotoxicity (ADCC)
 Attack:
 foreign cells
 virus-infected cells
 cancer cells
Lymphocyte Distribution
 Tissues maintain different T cell and B cell
populations:
 T Cells: high in blood, thymus, marrow, spleen, others
 B Cells: high in nodes, spleen, others
 Lymphocytes wander through tissues, migrating
throughout the body to defend peripheral tissues (T
cells move faster than B)
 Have long life span (4 years+, up to 30!)
 Retain their ability to divide, which is essential to
immune system function
Hi ! Take short rest!!
2- Organs of
the Immune System
Organs of Immune System
Primary
Bone marrow
Thymus gland
Secondary
Spleen
Lymph nodes
Tertiary
MALT
Lymphoid Organs & Tissues
 spleen, thymus gland,
 Lymph nodes and
tonsils
 Peyer’s patches and bits
of lymphatic tissue
scattered in connective
tissue
Figure 20.5
Primary lymphoid organs
Thymus
 Secretes hormones (thymosin and thymopoietin) that cause T
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lymphocytes to mature
It functions strictly in T lymphocyte maturation
It does not directly fight antigens
Located in mediastinum
Deteriorates after puberty
Divided into 2 thymic lobes
Septa divide lobes into smaller lobules
Each lobule contains:
 a dense outer cortex of dividing T cells
 a pale central medulla
 T cells:
 divide in the cortex
 migrate into medulla
 leave thymus by medullary blood vessels
Secondary lymphoid
organs & tissues
Lymphoid Functions
 Lymphoid tissues and lymph nodes:
 Distributed throughout body to monitor peripheral
infections respond before infections reach vital organs
of trunk
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Lymph nodules in mucosa
Lymph nodes monitor plasma/interstitial fluid
Spleen Monitor blood
 Structure
Spleen
 Gross
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Largest single collection of lymphoid tissue in the body
Ovoid organ in upper left quadrant of abdomen
 Microscopic
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Compartmentalized
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Periarticualr lymphoid sheath
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Red pulp
White pulp
Site of Ag presentation
Major cell types:
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Lymphocytes
Macrophages
Dendritic cells
RBCs
Functions of the Spleen
 Filters the blood like lymph nodes filter the lymph
 Phagocytes in the spleen remove abnormal blood cells
•
•
•
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and other blood components by phagocytosis
Storage of iron and other RBC products for later use
or elimination
Initiation of immune responses by B cells and T
cells in response to antigens in circulating blood
Site of lymphocyte proliferation
Stores RBC’s & platelets
Lymph Nodes
 Structure
 Gross
 Bean-shaped structures
 Drains major segments of lymphatic system
 Microscopic
 Major cell types
 Lymphocytes
 Macrophages
 Dendritic cells
 Cortex/paracortex/medulla
 Follicles
 Primary
 Secondary
Peripheral Lymph Node Structure
Lymph Nodes
Distribution
•cervical region
• axillary region
• inguinal region
• pelvic cavity
• abdominal cavity
• thoracic cavity
• supratrochlear region
Lymph Nodes
Functions:
 Filter potentially harmful particles from lymph
 Immune surveillance by macrophages and
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lymphocytes
Areas of lymphocyte production & proliferation
1st line of response to antigens
Secondary follicle (Germinal center) is site of B cell
proliferation & differentiation
After Ag stimualtion lymphocyte numbers increase
by 50X in efferent lymphatic vessel
(Lymphadenopathy)
Tertiary lymphoid tissues
Tonsils
 Follicular structure
 Contains lymphocytes, macrophages, mast cells
 Germinal centers appear in response to Ag
 Protective role in URI
Appendix
 Associated with intestines
 Responds to Ag
 Role in GI immune response
Mucosa Associated Lymphoid Tissues
(MALT)
 Lymphoid tissues below epithelium (Peyer’s Patches)
 Presence of B cells
 Ag presented through unique cell (M cell)
 Preferentially responds with IgA antibody
Next Lecture: Innate immunity
Write assay about
 Mucosa Associated Lymphoid Tissues
 Lymph Nodes
 Function of spleen
Assignment:
Cell Frequency of Different Leukocytes in
Blood of Healthy and diseased Individuals.