This document discusses the cells and organs of the immune system. It describes the primary and secondary lymphoid organs that support lymphocyte development and activation. The primary lymphoid organs are the thymus and bone marrow, which provide an environment for lymphocyte maturation. The secondary lymphoid organs, such as lymph nodes and spleen, are sites where mature lymphocytes encounter antigens. The document also outlines hematopoiesis, the process by which stem cells in the bone marrow differentiate into various immune cells through the influence of cytokines and growth factors in the bone marrow microenvironment.

1. Cells and Organs of the Immune system
Primary lymphoid
organs
Secondary lymphoid
organs
Organs of immune system
1.Thymus
2. Bone Marrow
1. Lymph Node
2. Spleen
3. MALT (Mucosal
Associated Lymphoid
Tissue)

2. Primary lymphoid
organs
provide environment
for the development and
Maturation of
Lymphocytes
Secondary
lymphoid
organs
Site where mature
lymphocytes act on
antigen

3. Interconnected by
1. Lymph
2. Blood

4. Formation of the cells of the immune system
-By Hematopoiesis
is the formation and development of
WBC’s and RBC’s
from HSC (Haematopoietic stem cell)

5. Stem cells
- differentiate into other cell types (multipotent,
or pluripotent)
- are self-renewing

6. Hematopoiesis
LTC-Ic- long-term colony-initiating cell and
CFC- colony-forming cells

9. No of HSC in BM
Few (1 in 5x104 BM cells)

10. Growth, maturation and Differentiation of
stem cells
Occurrence  Stromal cells of BM
Stromal cells include
fat cells
endothelial cells
fibroblasts and
macrophages.

11. Stromal cells
has HIM (haematopeietic inducing
environment)

Growth factors and cytokines

Growth and maturation of stem cells
produce

12. GM-CSF= Granulocyte Macrophage Colony Stimulating Factor;
IL= Interleukin
M-CSF= Macrophage Colony Stimulating Factor
SCF= Stem Cell Factor
Role of
cytokines in
differentiation

13. Growth factors (Haematopoietic growth factors)
1. Colony Stimulating Factor (CSF)
2. Erythropoietin
Colony Stimulating Factor (CSF)
(a family of acidic glycoproteins) including
1. Multilineage CSF ( or IL-3)
2. Macrophage CSF (M-CSF)
3. Granulocyte CSF (G-CSF)
4. Granulocyte Macrophage CSF
(GM-CSF)

14. Erythropoietin (a glycoprotein)

induces development of erythrocytes
and regulates the production of red blood cells.

15. Cells producing cytokines (Interleukins) for
differentiation
Stromal cells of BM
Activated TH cells
Activated macrophages
Cytokines
Eg., IL (interleukin)
TNF (tumour necrosis factor)
INF (interferon)

16. Regulation of hematopoiesis
Hematopoiesis is regulated so that
the levels of blood cells are maintained
This is done by a balance between the
number of
cells
removed by
cell death
and
the number that are
formed from
division and
differentiation

19. 1. Lymphoid cells T cells 4. Mast cells
B cells
NK cells
(Null cells)
2. Mononuclear
cells
Monocytes 5. Dendritic
cells
Langerhans cells
Interstitial DC
Macrophages Interdigitating
DC
Circulating DC
3. Granulocytic
cells
Neutrophils
Eosinophil
Basophil
Cells of the immune system

20. I. LYMPHOID CELLS ( T, B and NK cells)
Blood  20 – 40%
Lymph  99%
Humans have  1010 - 1012
lymphocytes in
the body

21. T and B cells  Not encountered Ag

Naive cells/Unprimed Cells/Resting Cells [Small and not fully
developed]

They will be in Go phase of cell cycle
 on Ag activation + Cytokines
enter into Early G1

Late G1

S Phase (DNA synthesis)
G2

M (Cell Division)

1. Effector cells 2. Memory Cells

22. Naïve
cell
Activated
cell
Ag +Cytokines
Effector cells
(Short life (few days –
Few Wks)
Memory cells
Long life span (life long
immunity)
B cell Lineage T cell Lineage
Plasma Cells TH Cells TC cells
Produce Ab

23. Naïve Cell
smaller in size (only
about 6 m in
diameter)
few mitochondria
a poorly developed
endoplasmic
reticulum and Golgi
apparatus
Naive lymphocytes (both T and B cells)

25. As they progress through the cell cycle,
lymphocytes enlarge into 15 m-diameter blast
cells, called lymphoblasts
these cells have a
higher cytoplasm:nucleus ratio and
more organellar complexity than small
lymphocytes

26. Plasma cells
# Are the antibody-
secreting effector cells
of the B cell Lineage
# They have a characteristic
cytoplasm that contains
abundant endoplasmic
reticulum (to support
their high rate of protein
synthesis) and also
many Golgi vesicles

27. Surface markers of Lymphoid cells
different surface markers to distinguish each cell
each specific for a particular type of lymphocytes

28. Identifying Cell Using the CD
Nomenclature
• CD- Cluster Of Differentiation
or Classification Determinant)
• Nearly 364 Human CD Markers
identified till Nov 2014
• Some play a role in signal transduction
• Some are involved in cell adhesion

29. B cells- CD19
NK cells- CD56
Monocytes/Macrophages- CD14
Dendritic Cells- CD1c
(Human), CD11c (mouse)
T cells- have CD4 or CD8 and CD3

31. B cell Markers Basophil Markers

32. Macrophage/Monocyte Markers