The document describes the key components of the immune system, including cells, molecules, tissues and organs. It discusses how cells such as T cells, B cells, and dendritic cells originate from hematopoietic stem cells in the bone marrow. It also outlines the major immune system molecules like cytokines, antibodies, and complement proteins. Key lymphoid organs that support immune responses are described, including the bone marrow, thymus, lymph nodes, spleen and mucosal-associated lymphoid tissues. Both innate and adaptive immunity are summarized.

1. COMPONENTS (MOLECULES, CELLS,
TISSUES, ORGANS) OF THE IMMUNE
SYSTEM
Presenter: Daniel Mwandu
Facilitator: Dr. A. Joachim

2. PRESENTATION OUTLINE
• Introduction
• Hematopoiesis
• Components of Immune System(Cells,
Molecules, Tissues and Organs)
• Immune response
• Application

3. LEARNING OBJECTIVE
At the end of this session trainee will be able to;
• Describe the Components of Immune System in
term of Cells, Molecules, Tissues and Organs.
• Explain the mechanism of Immune response.
• Explain the Clinical significance of the
knowledge of immune system

4. INTRODUCTION
• The immune system is a complex network of
organs, cells and proteins that defends the body
against infection or foreign substance, whilst
protecting the body's own cells
• It includes white blood cells and lymph system
organs and tissues.
• Immune response is the coordinated reaction
of the cells of the immune system to a pathogen
as well as to foreign, regardless of the
physiologic or pathologic consequence.

5. Introduction Conti..
• The physiologic function of the immune system is
defense against infectious microbes;
• however, even noninfectious foreign substances
and products of damaged cells can elicit immune
responses
• The component of immune system originate from
Hematopoiesis

6. HEMATOPOIESIS
• All blood cells arise from a type of cell called the
hematopoietic stem cell (HSC).
• Stem cells are cells that can differentiate into
other cell types; they are self-renewing—they
maintain their population level by cell division.
• They are two, unipotent cell and multipotent, or
pluripotent cell,
• Cells of the Immune system were derived from the
Pluripotent hematopoietic stem cell which can
differentiate into myeloid or lymphoid stem cells.

7. Hematopoiesis

9. COMPONENTS OF THE IMMUNE
SYSTEM
• Cells, Molecules, Tissues and Organs
provide non-specific and specific protection
against
– Microorganisms
– Microbial toxins
– Tumor cells
• Crucial to human survival

10. CELLS OF IMMUNE SYSTEM

11. Comparison of T and B cells
T-cells B-cells
Responsible for cell mediated
immunity
Responsible for Humoral immunity
Differentiate inside Thymus Gland Differentiate inside Bone Marrow
No surface antibodies , have other T
cell receptors. E.g TCR
Surface Antibodies present
Transformed in small lymphocytes by
antigens
Transformed to plasma cells by
antigens
Secrete Lymphokines Secrete antibodies
Sub populations: Tc, Th and
suppressor cells
Sub populations: memory cells and
plasma cells
Activate phagocytes and B-cells B-cells or plasma cells produce
antibodies

13. DENDRITIC CELLS (DC)
• Heterogeneous myeloid & lymphoid
origins
– Langerhans, interstitial, myeloid and
lymphoid DCs
• Best APC for presenting to naïve T-
cells
– express high levels of both MHC II
molecules and members of the co-
stimulatory B7 family
• Capture Ag in one place- then
migrate- present Ag in another
place to T lymphocytes.
• Immature to mature; change in
functionality from Ag capture to Ag
presentation
Kuby immunology

14. Kuby immunology

15. MOLECULES OF IMMUNE SYSTEM
 These are the major proteins of the immune system
are predominantly cytokines (a type of hormone
responsible for communication between cells of the
immune system), antibodies (immunoglobulins), and
complement proteins
 Soluble molecules including Cytokines, Interleukins,
antibodies, Complements and metabolites.
 Cell surface molecules including markers (CD),
receptors (BCR, TCR, MHCI, MHCII etc.), co stimulatory
molecules e.g. B7 family on DCs ,adhesion molecules
(integrins, selectins, mucins, etc.) and Tumour markers
e.g CEA 125

16. • Complements-A series of molecules or proteins
that work together to perform many immune
system functions
• Cytokines are secreted proteins that work as
mediators of immune and inflammatory reactions
– provide a mechanism of the immune system to
“talk” to one another to coordinate a response.
– Cytokines includes chemokines, interferons,
interleukins (ILs), lymphokines, and Tumor
necrosis factor

18. THE CLUSTER OF DIFFERENTIATION
(CD)
• Definition; CD is a group of cell surface marker
providing targets for immunophenotyping
• Importance of CD; as a cells marker used in immune
cell separation, identification and counting, also cell
receptors used in monitoring of the immune expression
profile of different CD antigens. For examples CD4
count marker of T-helper cell while CD8 counter of T-
cytotoxic cells.
• History; there was chaotic in naming monoclonal
antibodies(Mab) manufactured from different laboratories
before 1982.

19. CD cont..
Nomenclature;
• CD nomenclature was established in 1982 on 1st
International Workshop and Conference on Human
Leukocyte Differentiation Antigens (HLDA) held in Paris
• Protocol for identification and investigation of cell surface
molecules
• CD for humans is numbered up to 371 most recently (as
of 2016), making a total CD 401 because some CD
share the common chain or the same family gene.
• If the molecule has not been well-characterized, or has
only one monoclonal Ab, it is usually given the
provisional indicator "w" (as in "CDw186")

20. Kuby immunology

21. Organs of the Immune system

24. Primary lymphoid organs
Bone marrow
• Hematopoiesis/ development of myeloid and lymphoid
cells
• Origin and Maturation of B-cells
Thymus
• Epithelial cells (thymic stroma)
– forming a sponge-like meshwork of epithelial cells=
reticular epithelial cells
• T-cells- Lymphopoiesis (proliferate and mature)
• Mature T-lymphocytes leave via venules in the
medulla and travel through the blood to populate
peripheral organs
• If the thymus fails to form, T-cells do not develop and
no cell mediated immunity

25. Changes in Thymus with age

26. Secondary lymphoid organs
• Specialized for trapping antigen, facilitating
presentation to lymphocytes
• Characterized by:
–Localized areas for T-cells and B-cells
–lymphoid Follicles where B cells mature
• Include; Lymph nodes, Spleen and
MALT(mucosal associated lymphoid tissue)
includes Peyer’s patches, the tonsils, and the
appendix, etc

27. Lymph nodes
• Sites where immune responses are mounted to
antigens in lymph
• Filter Ag from lymph, Ags are processed by APCs
and presented to Th cells which become activated
• Present everywhere, but large and numerous ones
are found in certain sites: Axillary, groin (inguinal
LNs), near the abdominal aorta (coeliac LNs), in the
neck (cervical LNs) and in the mesentery
(mesenteric LNs)
• Regional nodes: draining particular regions or
organs

28. Lymph nodes

29. Spleen
• Plays a major role in
mounting immune
responses to antigens in
the blood stream
• While lymph nodes are
specialized for trapping
antigen from local tissues,
the spleen specializes in
filtering blood and trapping
blood-borne antigens
• It is smooth surfaced except
for hilus, where blood
vessels enter and leave .

31. TONSILS
• At entrance to GI tract:
• 1 pharangeal=
“adenoids”
• 2 tubal
• 2 palatine= “tonsils”
• 1 lingual
• Populated with
macrophages,
lymphocytes
granulocytes and mast
cells
• Defend against antigens
entering through the
nasal and oral epithelial
routes

32. • M cell (microfold cells) lining the surface of the
Peyer’s patch are specialized to uptake Ag from
the gut
• The lamina propria contains dense, diffuse
lymphoid tissue packed with some 200 lymphoid
follicles.
Peyer’s patch

33. Appendix
• Worm-like projection
of the human large
intestine, 10-15 cm
long and up to 8mm
in diameter.
• Store house for good
bacteria, rebooting
the digestive system
after diarrheal
illnesses.

34. Mucosal Immune System
MALT- Mucosal Associated Lymphoid Tissue
• Mucosal surfaces of mouth, respiratory and
reproductive tracts are colonized by
lymphocytes and accessory cells
• Respond to ingested, inhaled antigens
• Inlcudes:
– BALT (bronchial) :
– GALT (gut) :
• Tonsils
• Peyer’s Patches
• Appendix

35. Cutaneous-Associated Lymphoid Tissue
• skin is an important anatomic barrier to the external
environment
• keratinocytes- specialized epithelial cells on Outer
layer
– secrete a number of cytokines that may function
to induce a local inflammatory reaction
– can be induced to express MHC II molecules and
may function as APC
• Langerhans cells - a type of dendritic cell,
internalize antigen by phagocytosis or endocytosis

36. Cutaneous-Associated Lymphoid
Tissue
• Intra epidermal lymphocytes are similar to the
intraepithelial lymphocytes of MALT in that most of
them are suppresor-cytotoxic (CD8) T cells
– play a role in combating antigens that enter
through the skin
• Underlying dermal layer of the skin contains
scattered CD4 and CD8 T cells and macrophages

37. IMMUNE RESPONSE
• Defense against microbes is mediated by
sequential and coordinated responses that are
called Innate immunity and Acquired immunity.
• Innate immunity (also called natural immunity) is
essential for defending against microbes in the
first few hours or days after infection, before
adaptive immune responses have developed. It is
present from the point of birth while
• Acquired or Adaptive immunity develops over
growth.

38. INNATE IMMUNITY
• The principal components of innate immunity
are
(1) Physical and chemical barriers, such as
epithelia and antimicrobial chemicals produced
at epithelial surfaces;
(2) Phagocytic cells (neutrophils, macrophages),
dendritic cells (DCs), mast cells, natural killer
(NK cells) and mast cells;
(3) Blood proteins, including components of the
complement system and other mediators of
inflammation

39. ADAPTIVE IMMUNITY
• The adaptive immune response is mediated by
cells called lymphocytes and their products.
• Lymphocytes express highly diverse receptors
that are capable of recognizing a vast number of
antigens.
• B lymphocytes and T lymphocytes are two major
populations of lymphocytes which mediates
different types of adaptive immune responses.
• B lymphocytes mediates humoral adaptive
immunity and T lymphocytes mediates cell
mediated immunity

43. Features of immune system
• Specificity, Ability to distinguish differences among various
foreign molecules.
• Diversity, Recognize a vast variety of foreign molecules
• Discrimination between self and non self, to recognize and
responds to molecules that are foreign or non self
• Memory, Once a immune system has responded to an
antigen it exhibits memory and the second encounter the
same antigen induces a highest state of immune response.

44. Significance of the immune system

45. Significance of the immune system
• Development of Clinical laboratory techniques
for diagnosis and monitoring of various
diseases such as agglutination tests, flow
cytometry, immunoblotting etc
• Immunotherapy, new treatment strategies for
patients with immune disorders i.e cancer
• Immune system molecules such as cytokines
can serve as biomarkers of disease. For
example, the cytokines TNF-α, IL-1, and IL-6 in
the sera of patients with septic shock

46. Cells of the Immune System

48. THANK YOU

49. References
• Introduction to the immune system, Nomenclature,
General, Properties, and Components
• Immune SyKuby Immunology, 6th edition, 2007
• http://missinglink.ucsf.edu/lm/immunology_module/prol
ogue/objectives/obj01.html
• https://www.tcd.ie/Biology_Teaching_Centre/assets/pdf/b
y2209/co'fby2209.2012-lecture6.pdf
• Bonnie Hylander,
Ph.Dhttps://www.roswellpark.edu/sites/default/files/hyla
nder_2014_intro_to_immunol_rpci_aug_28_cells_and_tiss
ues_lecture-_revised.pdf