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Cells of the Immune System.pptx
1. Bernard S. Bagaya, PhD
Lecturer
Dept. Immun & Mol. Biol
Sch. Biomedical Sciences
MakCHS Organs, Tissues
and Cells of the
Immune
System
Lillian Namuli, MSc.
Teaching Assistant
Immunology
3. The Bone marrow
• Soft tissue in center of
bones
• Site of hematopoiesis in
mammals; all blood cells
originate in the bone
marrow
• Rich in hematopoietic
stem cells – progenitors
of all immune cells
• Site of B cell development
4. The Thymus
• Located behind the
sternum, in front of heart
• Two identically sized lobes
• Larger in childhood, shrinks
in adulthood
• T cell precursors migrate
from bone marrow to
thymus
• Site for T cell differentiation
and maturation
• Also synthesizes hormones
(thymosin, thymolin) that
influence lymphocytes in
blood stream
5. The Lymphatic system
The Lyphatic System
-collects and transports particulates
to lymph nodes for
filtering/sampling
6. Lymph node
- first organized lymphoid
structure to encounter Ag
that enter tissue spaces
- filters tissues
7. The Lymph nodes
• Distributed widely in the body
• Highly packed with lymphocytes (B and T cell follicles),
APCs (Macrophages and Dentritic cells)
• Trap and filter particulates from tissues, hence located
along lymphatic vessels
• Rich network of blood capillaries; bring in and take out
immune cells and effector molecules
• Optimal environment for antigen encounter, antigen
presentation, activation, proliferation, TH cell help
• Cortex (outer layer) is packed with B cells and Germinal
centers (differentiating/proliferating B cells)
• Medulla contains plasma cells secreting antibodies
9. The spleen
• Filters particulates in blood
• Consists of the red pulp and white pulp
• White pulp packed with B lymphocytes and T
cells; the PALS contains mostly T-cells
• Antigen activated B cells proliferate and form
Germinal centers in White pulp
15. GCs: Site of B cell antigen-dependent proliferation,
somatic hypermutation and affinity maturation
• GCs are anatomically distinct structures within
secondary lymphoid organs
• Formed by packing of rapidly proliferating B
cells
• Rich in antigen/antigen-laden APCs
• Consists of the Light zone and the Dark zone
– Dark zone- rapidly dividing B cells (Centrocytes)
– Light Zone- B cells undergoing affinity selection
(centroblasts), FDCs, Th-cells.
21. How can they be distinguished from
each other?
Cell Surface Molecules
Cluster of Differentiation (CD) e.g CD4, CD8
Functions (secreting soluble
factors)
23. B cells
- Part of the Adaptive immunity
- Originate/develop in Bone Marrow (humans, mice)
- recognizes antigen directly by cognate interaction with membrane
bound antibody (BCR)
- becomes antibody producing plasma cells or Memory B cell
Memory cells
24. Total B cells: CD45+, B220+, CD19+, CD20+
Naive B cells: CD19+, IgD+/IgM+, CD10+
Mature B cells: CD19+, CD20-, IgG+
Memory B cells: CD19+, CD27+, IgM+
A few B cell markers used in flow cytometry
25. T cells- originates in the BM, matures in the thymus &
circulates via blood to secondary lymphoid organs
- T cells recognize Ag only when it is bound to MHC on
the surface of APC
- CD4 TH cells secrete cytokines
- CD8 TC cells kills aberrant self cells
- Both CD4 TH and CD8 TC cells have long term memory
26. NK cells
• Part of Innate Immunity
•expresses CD16 and CD56 receptors
• Highly Cytotoxic; kills virus infected cells and
tumor cells
• kills antibody bound cells - ADCC
• secrete soluble factors (cytokines) responsible
for immune activation
34. - blood
Granulocyte-monocyte
progenitors (BM)
differentiate into
promonocyte
leave BM to enter into
circulation
differentiate into mature
monocytes
Migrate into tissues to
become tissue-specific
macrophages
resident
wandering
Hematopoeitic Stem
cells (BM)
