This document provides an overview of immunology and the immune system. It discusses the types of immunity, including innate and adaptive immunity. It describes the lymphoid organs such as the thymus and bone marrow that are involved in immune cell development. The major cells of the immune system are described, including mononuclear phagocytes, lymphocytes, and their B cell and T cell subsets. Both humoral and cellular immune responses are summarized. Key terms related to immunology and the immune system are also defined.

1. Immunology

2. • Immunity and Immunology
• Related lingoes
• Types of Immunity
• Lymphoid organs
• Types of Immune responses
• Cells of Immune System
TopicsTopics

3. What is Immunity????
( Latin: Immunis = "to make safe“)
The resistance of the host body towards
the pathogenic microbe and its toxin is
called as Immunity!!!!!

4. Immunology
•It is a broad branch of biomedical science that
covers the study of all aspects of the immune
system in all organisms.
• It deals with–
the physiological functioning of the immune
system in states of both health and disease;
malfunctions of the immune system in
immunological disorders;
the physical, chemical and physiological
characteristics of the components of the immune
system in vitro, in situ, and in vivo.

5. Father of Immunology
Edward Jenner!!!!!
He was an English country
doctor who pioneered
vaccination.
 Jenner's discovery in 1796
that inoculation with cowpox
gave immunity to smallpox,
was an immense medical
breakthrough and has saved
countless lives.

6. Related Lingoes

7. Pathogen vs. Antigen
• Pathogen- Microorganism that can cause
disease.
• Antigen- (Foreign substances; Non-self
materials) It is not an organism, but rather,
a molecule attached to a foreign organism
that activates an antibody response.
Organic compounds with high molecular
weight.

8. • Interferons – Polypeptides synthesized upon
viral infection of a cell and act as a messengers
that protect normal cells in the vicinity of infected
cells from becoming infected.
3 major categories- IFN- alpha , beta, gamma.
• Cytokine/Lymphokine/Chemokine – Growth
factors specialized to control cell division and
differentiation in the immune system.
• TCR(T cell receptor) – Membrane bound antigen
receptor on T-cells that can only recognize the
antigen being presented by a cell membrane
bound protein called MHC (Major
histocompatibility complex).

9. • CD- stands for cluster of differentiation,
which indicates a defined subset of
cellular surface receptors (epitopes) that
identify cell type and stage of differentiation,
and which are recognized by antibodies.
More than 250 identified clusters, coating the
surface of B lymphocytes and T
lymphocytes.
• Monoclonal antibodies – are homogenous
immunological reagents of defined specificity
,so that these can be utilized for diagnosis
and screening with ease and certainty .

10. Complement System
• Paul Ehrlich coined the term and defined it
as “the activity of blood serum that completes
the action of the antibody”.
• It is a major triggered enzyme plasma
system.
• It coats microbes with molecules that make
them more susceptible to engulfment by
phagocytes.
• Affects both innate and adaptive immunity.

11. • Vascular permeability mediators increase the
permeability of the capillaries to allow more
plasma and complement fluid to flow to the
site of infection.
• The principle actors in this system are 11
proteins designated C1 to C9.

12. Immune systemImmune system

13. Innate (non-specific)
immunity
• Anatomic barriers
(Skin,mucous
membranes)
• Physological barriers
(temperature, pH)
• Phagocytic Barriers
(cells that eat
invaders)
• Inflammatory barriers
(redness, swelling,
heat and pain)
Adaptive (specific)
immunity
• Antigen specificity
• Diversity
• Immunological
memory
• Self/nonself
recognition

15. Fluid systems in body
There are two main fluid systems in
the body:
•blood
•lymph.

16. • Blood - The fluid consisting of plasma, blood cells,
and platelets that is circulated by the heart through
the vertebrate vascular system, carrying oxygen and
nutrients to and waste materials away from all body
tissues.
• Lymph – Blood – RBCs…..
Prominent among the constituents of lymph
are lymphocytes and macrophages, the primary
cells of the immune system with which the body
defends itself from invasion by foreign
microorganisms.
Lymph is conveyed from the tissues to the venous
bloodstream via the lymphatic vessels. On the way,
it is filtered through the lymphatic organs (spleen
and thymus) and lymph nodes.

17. Lymphoid
Organs

18. Lymphoid Organs
Primary
 Provide appropriate
environment for
lymphocyte maturation.
 Thymus and Bone
marrow.
Secondary
 Trap antigens and make
it available for mature
lymphocytes.
 Lymph nodes, and
lymphoid follicles
in tonsils, Peyer's
patches, spleen,
adenoids,etc. associated
with the mucosa-
associated lymphoid
tissue (MALT).

19. Thymus
• Situated in the center of the
upper chest just behind
the sternum.
• Bilobed structure.
• Zonated into many lobules,
seperated from each other
by connective tissue strands
called trabeculae.
• Each lobule consists of
inner medulla and outer
cortex.

20. •Develops in embryonic life as an outgrowth
of a structure known as the 3rd
branchial
pouch invaded by lymphoid stem cells.
•Thymocytes (T-cells) mature in medulla.
•The majority of lymphocyte production
happens early in life, so the thymus gland
deteriorates with age. In youth, the thymus
will reach the size of an apple, but it is
reduced to the size of a small marble in the
elderly.

21. Bone Marrow
• Bone marrow is the flexible tissue
found in the hollow interior of bones. In
adults, marrow in large bones produces
new blood cells. It constitutes 4% of total
body weight, i.e. approximately 2.6 kg
(5.7 lbs.) in adults.
• Marrow types-There are two types of
bone marrow: red marrow (consisting
mainly of hematopoietic tissue) and
yellow marrow (consisting mainly of fat
cells). Red blood cells, platelets and
most white blood cells arise in red
marrow. Both types of bone marrow
contain numerous blood vessels and
capillaries.

22. • Hematopoietic stem cells give rise to the three
classes of blood cells that are found in the
circulation: white blood cells (leukocytes), red
blood cells (erythrocytes), and platelets
(thrombocytes).
• Mesenchymal stem cells are found arrayed
around the central sinus in the bone marrow.
They have the capability to differentiate into
osteoblasts, chondrocytes, myocytes, and many
other types of cells. They also function as
"gatekeeper" cells of the bone marrow.

23. Immune systemImmune system
express their specificexpress their specific
activity in two mainactivity in two main
ways………….ways………….

24. Humoral immune
response
Lymphocyte produce
antibodies in response
to certain specific
antigens
Antibody binds to
antigen and destroy by
variety of mechanism
B-cells are responsible!
Cellular immune
response
Lymphocyte and
Macrophages
cooperate
Direct Destruction of
pathogenic
organisms
T-cells are responsible!

26. Cells of Immune
system

28. Mononuclear Phagocytes
•Consists of monocytes and macrophages.
•Monocytes circulate in the bloodstream for 8
hrs., during this time they enlarge and migrate
into tissue spaces to differentiate into
macrophages.
•Activity is enhanced by Cytokines.
•Activated macrophages serve as antigen
presenting cells by expressing higher level of
ClassII MHC.
•Two types- Fixed and Free/ Wandering
Macrophages.

29. Fixed macrophages-
• Kupffer cells – Liver
• Alveolar macrophages – Lung
• Histiocytes – Connective tissue
• Osteoclasts – Bone
• Mesangial cells – Kidney
• Microglial cells – Brain

30. Phagocytosis

31. Types of Mononuclear
Phagocytes
1.Granulocytes
• Neutrophil- Multilobed
nucleus; phagocytic.
• Eosinophil - Resemble
neutrophils; defense
against Parasitic
organisms; phagocytic
• Basophil – Non-
phagocytic; release
pharmacologically active
mediators found in their
granules leading to
allergies.
2. Agranulocytes
• Lymphocytes
• Monocytes

32. Monocytes
• Largest corpuscle of blood.
• There are at least three types of monocytes
in human blood :
• a) the classical monocyte : CD14++ CD16-
monocyte.
• b) the non-classical monocyte :
CD14+CD16++ monocyte.
• c) the intermediate monocyte CD14+
+CD16+ monocytes.

33. Lymphocytes
• Chief cells of immune system.
• In blood= 20-40% and in lymph=99%.
• Continuously circulate in blood and lymph.
• Capable of migrating into the tissue
spaces and lymphoid organs.
• Non-phagocytic, motile cells.
• Three main forms:- T-cells, B-cells, Null
cells.

34. B or T cells that have not come in contact with
antigen =Naïve/Resting/Unprunned cells.
Lymphocyte (Naïve cells)
Lymphoblasts
Effector Cells [Plasma (B-cell); TH(T-cells)]
or
Memory Cells

35. T-cellsT-cells
• Derive their name Thymocytes from the
site of maturation i.e. thymus.
• Arise from the hematopoietic stem cells in
the bone marrow and later migrate to the
thymus gland to mature.
• Three types–
1.T-Helper (TH)
2.T- Cytotoxic(TC)
3.T-Suppressor(Ts)

36. 1. T-Helper (TH) - Display CD4 glycoprotein
Recognise and interact with the antigen
presented on ClassII MHC molecule on APC.
TH gets activated and undergoes
extensive proliferation
Daughter cells called Effector cells
produced

37. • Specific Cytokines secreted and generate
specific immune response
• TH1 Response TH2 Response
Tc ,Macrophages B cells
activation
activation

38. 2. T-Cytotoxic cells –
• Activated under the influence of cytokines
produced by TH cells and antigen
interaction presented on Class I MHC.
• Differentiation into an effector cells CTLs/
Cytotoxic T Lymphocytes.
• Possess Cytotoxic activity.

39. 3. T-Suppressor cells –
• Play important role in suppression of
humoral and cell-mediated immune
response
• But not isolated so far.

40. B-cellsB-cells
• Derived their name from the site of
maturation in birds Bursa of Fabricius.
• Mature in Bone marrow
• Leave bone marrow by expressing a unique
antigen binding receptor mIgM.
Naïve B cells + Antigen
Effector B cells Memory B cells
or
Plasma cells

41. Immunoglobulins (Ig)
• Antibodies, also called immunoglobulins or
Igs constitute the gamma globulin part of the blood
proteins.
• Soluble proteins secreted by the plasma offspring
(clones) B cells.
• The antibodies inactivate antigens by
(a) complement fixation (proteins attach to antigen
surface and cause holes to form, i.e., cell lysis),
(b) neutralization (binding to specific sites to prevent
attachment),
• (c) agglutination (clumping),
• (d) precipitation (forcing insolubility and settling out of
solution).

42. •The upper part or Fab
(antigen binding) portion
of the antibody molecule
attaches to specific
proteins [called
epitopes] on the antigen.
Thus antibody recognizes
the epitope and not the
entire antigen.
•The Fc region is
crystallizable and is
responsible for effector
functions, i.e., the end to
which immune cells can
attach.

43. • Constituents of gamma globulin are:
 IgG--76%,
 IgA--15%,
 IgM--8%,
 IgD--1%, and
 IgE--0.002%

45. -- IgM is the dominant antibody produced in
primary immune responses, First antibody
secreted; promotes agglutination and
precipitation reactions and activates
complement.
-- IgG is the only antibody that can cross the
placental barrier and responsible for the 3-6
month immune protection of infants; Major
antibody secreted during the secondary
response;neutralises antigens and
promotes phagocytosis and Activates
complement.

46. -- IgD is present only on surface of B cells,
serve as antigen receptor and plays an
important role in lymphocyte
differentiation.
-- IgA Most abundant form in body
secretions; high density in MALT.
-- IgE Fc binds to mast cells and basophils;
allergen binding to V regions promotes the
release of mediators, which triggers
allergic reactions.

47. Null CellsNull Cells
• Cytotoxic.
• NK cells belong to this group.
• Small granules in their cytoplasm contain
proteins such as perforin and proteases known
as granzymes.
• Upon release in close proximity to a cell slated
for killing, perforin forms pores in the cell
membrane of the target cell, creating an aqueous
channel through which the granzymes and
associated molecules can enter, inducing
either apoptosis or osmotic cell lysis.
• NK cells are activated in response
to interferons or macrophage-derived cytokines.

48. Dendritic cells
• Dendritic cells are covered with a maze
of membranous processes that look like
nerve cell dendrites.
• Most of them are highly efficient antigen
presenting cells.
• There are four basic types: Langerhans
cells, interstitial dendritic cells,
interdigitating dendritic cells, and
circulating dendritic cells.

49. Thank youThank you