Introduction to Immunity and the Immune system

The immune system is a complex network of organs, cells and proteins that defends the body against infection, whilst protecting the body's own cells. The immune system keeps a record of every germ (microbe) it has ever defeated so it can recognize and destroy the microbe quickly if it enters the body again.

1. INTRODUCTION TO
IMMUNITY AND THE
IMMUNE SYSTEM
PHINMA-CAGAYAN DE ORO COLLEGE | 2024

2. After finishing this chapter, you should be able to:
Discuss how immunology as a science began with the study of immunity.1.
Describe what is meant by an attenuated vaccine.2.
Explain how the controversy over humoral versus cellular immunity contributed to
expanding knowledge in the field of immunology.
3.
Contrast innate and adaptive immunity.4.
Describe the types of white blood cells (WBCs) capable of phagocytosis.5.
Discuss the roles of macrophages, mast cells, and dendritic cells in the immune system.6.
Identify the two primary and a secondary follicle.7.
List four secondary lymphoid organs and discuss their overall importance to immunity.8.
Described the function and architecture of a lymph node.9.
Compare a primary and a secondary follicle.10.
Define “cluster of differentiation” (CD).11.
Differentiate the roles of T cells and B cells in the immune response.12.
Discuss how natural killer (NK) cells differ from T lymphocytes.13.
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
LEARNING OUTCOMES
1

3. Cells of the Adaptive Immune System
B cells and Plasma Cells
T cells
Innate Lymphoid Cells and Natural Killer Cells
Organs of the Immune System
Primary Lymphoid Organs
Secondary Lymphoid Organs
2
CHAPTER 1 OUTLINE
IMMUNITY AND IMMUNIZATION
INNATE VERSUS ADAPTIVE IMMUNITY
CELLS OF THE INNATE IMMUNE SYSTEM
Leukocytes in Peripheral Blood
Tissue Cells
PHINMA-CAGAYAN DE ORO COLLEGE | 2024

4. 3
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
The study of the host’s reactions when foreign substances are introduced into the body.
HISTORY: IMMUNOLOGY
1st written records of immunological
experimentation (1500s), when the Chinese
developed a practice of inhaling powder made
from smallpox scabs in order to produce protection
This practice of deliberately exposing an individual
to material from smallpox lesions was known as
variolation.
Attenuation - takes an infectious agent and
alters it so that it becomes harmless or less
virulent.

5. 4
HISTORY: IMMUNOLOGY
Edward Jenner
Elie Metchnikoff Louis Pasteur
Almroth Wright
(1700s) discovered a remarkable
relationship between exposure to
COWPOX & IMMUNITY to SMALLPOX.
Paved the road to the development of
VACCINATION from VACCA (L. for COW)
(1800s) began to identify the
mechanisms that produce
immunity in the host
Phagocytosis - cells that eat cells
(1903) CELLULAR & HUMORAL
elements of the IS
The father of Immunology
PHINMA-CAGAYAN DE ORO COLLEGE | 2024

6. 5
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Immunity
The condition of being resistant to infection
Immunity (protection) by immunization is similar to the immunity a person
would get from disease, but instead of getting the disease you get a vaccine.
Immunization
Immunization is the process of giving a vaccine to a person to protect them
against disease.
Prevents diseases such as smallpox, polio, diphtheria and measles through
development of vaccine

7. 6
PHINMA-CAGAYAN DE ORO COLLEGE | 2024

8. 7
Cells of the Innate Immune System
PHINMA-CAGAYAN DE ORO COLLEGE | 2024

9. 8
Cells of the Innate Immune System
Play a key role in both innate and adaptive immunity.
Leukocytes defend against invasion by bacteria, viruses, fungi, and other foreign
substances
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
All blood cells arise from a type of cell called hematopoietic stem cells
Common myeloid precursors (CMPs) - polymorphonuclear cells (neutrophils,
basophils, and eosinophils), monocytes and macrophages, microglia, dendritic
cells, osteoclasts and mast cells.
Common lymphoid precursors (CLPs) - precursors to other mature blood cell types,
including: T-cells/T-lymphocytes

10. 9
Cells of the Innate Immune System
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Nuetrophils
Eosinophils
Polymorphonuclear
neutrophilic (PMN)
50% to 70% WBC in
adults
10 to 15 um in d
1% to 4% WBC in
non-allergic person
10 to 15 um in d
First responder at the
site of infection or
trauma
Rapidly kill invading microbes is
indispensable for maintaining host
health.
Release toxins that kills
bacteria and parasites
but also cause tissue
damage

11. 10
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Basophils Monocytes
less than 1% WBC
10 to 15 um in d
Cells of the Innate Immune System
Responsible for
defense against
parasites.
Release histamines that cause
inflammation and may be
responsible for allergic reactions
2% to 10% WBC
12 to 20 um (largest cell)
Stays in peripheral blood
for 30 hours
Migrate to the tissues and
become known as macrophages

12. 11
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
TISSUE CELLS
Macrophages
Specialized cells involved in the
detection, phagocytosis and
destruction of bacteria and other
harmful organisms.
They are a diverse phenotype of
professional phagocytic cells derived
from bone marrow precursors and
parent monocytes in the peripheral
blood.

13. 12
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
TISSUE CELLS
Macrophages
Alveolar macrophage: Lung alveoli - Phagocytosis of small particles, dead cells or bacteria. Initiation and
control of immunity to respiratory pathogens.
1.
Histiocytes: Connective Tissue - Motile, phagocytic cells found in the loose connective tissue throughout
the body, help the body heal after an injury or infection by removing dead cells, blood, micro-organisms
(such as bacteria and fungus), and foreign material from the body.
2.
Osteoclasts: Bone - Mediators of the continuous destruction of bone3.
Interstitial macrophage (IM): gut - represent the largest pool of tissue macrophages in the body4.
Kupffer cells: Liver- Initiate immune responses and hepatic tissue remodeling. Kupffer cells are the most
abundant tissue macrophages as they constitute 80-90% of them.
5.
Microglia: Central nervous system - Elimination of old or dead neurons and control of immunity in the
brain.
6.
Splenic macrophages (marginal zone, metallophilic and red pulp macrophages): Spleen marginal zone, red
and white pulp - Elimination of dysfunctional or old red blood cells
7.

14. 13
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Mast Cells
Mast cells are well-known for releasing histamine during
allergic reactions, such as pollen or insect sting allergies .
Plays a role in inflammation, help defend against pathogens
and are involved in wound healing and tissue repair.
Mast cells are distributed throughout the body in a wide
variety of tissues such as skin, connective tissue, and the
mucosal epithelial tissue of the respiratory, genitourinary,
and digestive tracts.

15. 14
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Dendritic Cells
Discovered by Steinman and Cohn in 1973.
Dendritic cells present the antigen to T lymphocytes to
initiate the adaptive immune response in a similar way as
macrophages.
Considered the most effective APC in the
body, as well as the most potent phagocytic cell.
Presents antigens on its surface, thereby triggered
adaptive immunity

16. 15
Lymphocytes - the key cell in adaptive immune
response
represents between 20% and 40% circulating
in WBCs
7-10 μm in diameter (typical small lymphocyte
and has a large rounded nucleus)
Cells of the Adaptive Immune System
has three (3) major populations; T cells, B cells, and innate lymphoid cells (natural
killer [NK] cells, prominent type) and they are difficult to distinguish visually
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
In the peripheral blood of adults; 10% to 20% are B cells, 61% to 80% are T cells, and
10% to 15% are NK cells.

17. 16
Cells of the Adaptive Immune System
In order to standardize the nomenclature, scientists set up
the Human Leukocyte Differentiation Antigens Workshops to
relate research findings.
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Panels of antibodies from different laboratories were used for
analysis, and antibodies reacting similarly with standard cell
lines were said to define “CLUSTERS OF DIFFERENTIATION”

18. 17
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
T CELLS
Develop in the thymus
Found in lymph nodes, thoracic duct
60%-80% of circulating lymphocytes in blood
Adaptive immunity: end products of activation are cytokines
antigens include CD2, CD3, CD4, and CD8
Develop in the bone marrow
Found in the bone marrow, spleen, lymph nodes; 10%-20%
of circulating lymphocytes in blood
Adaptive immunity: end product of activation is antibody
Antigens include CD19, CD20, CD21, surface antibody
B CELLS

19. 18
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Develop in the bone marrow
Found in spleen, liver; 10& to 15% of circulating lymphoid cells in blood
Bridge innate and adaptive immunity: lysis of virally infected cells and
tumor cells
Antigens include CD16, CD56
NK CELLS

20. 19
PHINMA-CAGAYAN DE ORO COLLEGE | 2024

21. 20
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Organs of the Immune System
Primary
Lymphoid Organs
Secondary
Lymphoid Organs
Bone Marrow
Thymus
Spleen
Lymph nodes
Other secondary lymphoid organ:
MALT
CALT

22. 21
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Bone Marrow - It can be considered
the largest tissue of the body, with a
total weight of 1300 to 1500 g in the
adult.
Organs of the Immune System
it is the main source of hematopoietic stem cells: (which develop into
erythrocytes, granulocytes, monocytes, platelets, & lymphocytes)
T, B, & NK cells arise from a common precursor known as the common lymphoid
precursor (CLP
Primary Lymphoid Organs
BONE MARROW

23. 22
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
Thymus - is a small, flat, bilobed organ found
in the thorax, or chest cavity, right below the
thyroid gland & overlying the heart
Organs of the Immune System
Primary Lymphoid Organs
THYMUS
Weight: 30g at birth, 35g at puberty
It was first presumed that early in
life, the thymus produces enough
virgin T lymphocytes to seed the
entire immune system.
However, new evidence indicates that although the thymus
diminishes in size, it is still capable of producing T lymphocytes
until at least the 5th or 6th decade of life.

24. 23
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
the largest secondary lymphoid organ
Blood reservoir
FILTERS BLOOD instead of LYMPH
DESTROY worn-out RBCs
Length: 12 cm | Weight: 150 g
Organs of the Immune System
location: the upper-left quadrant of the abdomen, just below the
diaphragm & surrounded by a dense connective tissue capsule
Secondary Lymphoid Organs
SPLEEN
WHITE PULP: is the lymphatic tissue surrounding
the arteries within the spleen (lymphocytes: T, B)
RED PULP: Is the lymphatic tissue associated with
the veins (fibrous network, filled with
macrophages & RBCs)
it is also the LARGEST SINGLE MASS of LYMPHATIC
TISSUE in the body
Within the RED PULP, 3 functions of the spleen are:
Macrophages remove ruptured, worn – out or defective
blood cells
1.
Storage of platelets (1/3 of total body supply)2.
Hemopoiesis during fetal life3.

25. 24
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
filter substances that travel through the lymphatic
fluid, and they contain lymphocytes (white blood
cells) that help the body fight infection and disease.
located along LYMPHATIC DUCTS, are about 600+
bean shaped structures
Are usually in groups: mammary, axillae and groin
Are capsulated like the thymus
Length: 1-25mm
Organs of the Immune System
Secondary Lymphoid Organs
LYMPH NODES
FXN: CENTRAL COLLECTING POINTS for LYMPH from
adjacent tissues (filtration

26. 25
PHINMA-CAGAYAN DE ORO COLLEGE | 2024
MALT (mucosal - associated
lymphoid tissue)
OTHER SECONDARY LYMPHOID ORGANS
Here, macrophages & lymphocytes are localized at some of the main ports of
entry for foreign organisms
CALT (cutaneous-associated
lymphoid tissue)
found in the gastrointestinal.
respiratory, and urogenital
tracts.=
=
protection of the ocular surface
by initiating and regulating
immune responses

27. THANK YOU
Presented By :
Kaye Gardner
Louise Brylle Balatayo
PHINMA-CAGAYAN DE ORO COLLEGE | 2024