Immune system plays an important role in safeguarding the organisms from pathological and allergic invaders. This is a brief presentation of explanation of role cells and organs in the immune mechanism. The slides are all about lymphocytes, phagocytes, monocytes, thymus, spleen, and some WBCs

1. Cells and organs of the
Immune System
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3. Introduction
 Immune system is the natural defense system
working in coordination with every other body
systems.
 Nevertheless, some of the body systems such as
blood and circulatory system, endocrinal system
and integumentary system work closely with
immune system.
 Our immune system encompasses both specific and
nonspecific components that have distinct yet
overlapping functions.
 Immune system works predominantly with its
memory system by using antibody-mediated and
cell-mediated immune responses.
Conti…………..

4. Cont……..
 These 2 systems develop the ability to
detect the new entry of microbes and
allergens; antigens.
 For immune system to function normally,
the immune cells must recognize, specify,
and develop a clear memory of nature of
antigens.
 Before moving on to the cells of immune
system, it is important to understand the
components and physiology of normal
immunity which helps to make things clear
about the pathophysiology of diseases of
the immune system.

5. Major components of immune system
Immune system is mediated by a group
of cells and organs distributed across
body systems. In addition, immunity is
also assisted by some specific organs
such as thymus, bones (bone marrow)
lymphoid tissues and some glands.

6. Cell-mediated immune system
The major cellular components of the immune
system are the monocytes, macrophages,
lymphocytes, and the family of WBCS or
granulocytic cells that includes neutrophils,
eosinophils, and basophils. Furthermore,
mononuclear phagocytes play a principal role
in the immune responses.

7. Role of macrophages
 Tissue macrophages are derived from
monocytes- a type of blood cells. In response to
antigenic stimulation, macrophages gets
activated to engulf the antigen and the process
is known as phagocytosis.
 Activated macrophages secrete proteolytic
enzymes superoxide anion and other oxygen
radicals.
 A number of epithelial dendritic cells; a part of
monocyte lineage works to process and
transport the antigens from skin, respiratory,
and stomach towards the regional lymphoid
tissues.

8. Role of lymphocytes
 Lymphocytes aids in the specific recognition
of antigen through immunologic memory.
They are of 2 categories, I, e bursa-derived
(B-lymphocytes) and thymus-derived (T-
lymphocytes).
 On an average, about 75% of circulating
blood lymphocytes are made up of T-
lymphocytes with the rest 10-15% being B-
lymphocytes while the remainder belongs to
neither B nor T lymphocytes

9. Role of null cells
Null cells are called natural killer (NK)
cells which are distinct from other
lymphocytes as they are slightly larger
and appears like kidney-shaped cells.

10. Role of neutrophils
Polymorphonuclear leukocytes are otherwise
known as neutrophils. They are granulocytic
cells derived from the bone marrow and
circulate in blood and tissue. They work by
phagocytosis and destruction of foreign
particles and organisms. The process is helped
by their cytoplasmic granular enzymes that
are in nature.

11. Role of Eosinophils
Eosinophils are often found in inflammatory
sites. Though neutrophils, eosinophils perform
many shared functions but eosinophils are less
efficient than neutrophils when it comes to
phagocytosis. Eosinophils.

12. Role of Basophils
Basophils are necessary for both immediate-
and late-phase allergic responses. They
release potent mediators of allergic
inflammatory diseases. Some of them are
histamine, leukotrienes, prostaglandins, and
platelet-activating factor ( PAF). All these
together influence the vascular system to
develop inflammatory response. Basophils
found in the circulation develops affinity
towards receptors for I.e. thereby help in
immediate hypersensitivity (allergic)
responses.

13. Organs of the Immune System
 Apart from cellular defense mechanisms,
many tissues and organs play their roles in
the immune mechanism .
 In mammals, the primary lymphoid organs
are the thymus and the bone (bone
marrow).
 Almost all the cells of the immune system
are originally derived from bone marrow.
Bone marrow contains pluripotent stem cells
hat differentiate themselves into
lymphocytes, granulocytes, monocytes,
erythrocytes, and megakaryocytes.

14. Thymus and the immune system
 The thymus helps to produce T-lymphocytes
and is the site of initial T-lymphocyte
differentiation. Its reticular structure allows
a significant number of lymphocytes to
migrate through it to become actively
immunocompetent against the antigens.
 Thymus develops T-cells in the thymic
cortex. The thymus regulates immune
function through the secretion of multiple
hormones that promote T-lymphocyte
differentiation

15. Role of lymph nodes, spleen and gut
 The lymph nodes, spleen, and gut-associated
lymphoid tissue are connected by blood and
lymphatic vessels.
 Through these vessels, lymphocytes circulate
towards the antigens, and spread the
specific experience of this antigen exposure
to all parts of the lymphoid system.
 Lymph nodes are scattered systematically
throughout the vasculature and are the
principal organs of the immune system that
localize and prevent the spread of
infection.

16. Lymph nodes
Lymph nodes on the other hand have a framework of
reticular cells and fibers that are arranged into a
cortex and medulla.

17. Spleen
 The spleen help to filter and process the
antigens from the blood.
 Some of the gut-associated lymphoid tissues
are tonsils, Payer’s patches of the small
intestine, and the appendix. .these cells
participate in mucosal immune responses
that generates antigen-specific IgA.

18. Inflammatory Mediators
 Mediators are released during immune
responses to coordinate and regulate
immune cell activities to generate
physiological or cytotoxic responses.
 They produce plasma proteins that are
activated by immune complex
(antigen-antibody) formation.

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