This document provides an overview of immunology and the immune system. It discusses the history of immunology including the discoveries of Metchnikoff, Behring, and Fleming. It also describes the innate and adaptive immune system. The main cells of the immune system are B cells, T cells, and natural killer cells. T cells can be classified as T helper cells, T cytotoxic cells, and T suppressor cells. The primary lymphoid organs are the bone marrow and thymus. Secondary lymphoid organs include the lymph nodes, spleen, Peyer's patches, and mucosa-associated lymphoid tissue.

1. Archana Soni
Assistant Professor
Shri Shankaracharya
Mahavidyalaya, Junwani
Bhilai (C. G.) INDIA

2. CONTENTS
1] Introduction
2] History of immunology
3] Innate and adeptive immunology
4] Cells of the immune system
a] B-Cell
b]T-Cell
c] Natural killer cells
5] Organ of immune system
a] Primary limphoid organ
b] Bone marrow
c] Thymus
d] Secondary lymphoid organ
e] Lymph nodes
f] Spleen
g] Payers patches
h ] MALT,GALT.

3. INTRODUCTION
-Immunology deals with the study of immunity and
immune systems of vertebrates .
-Immunity broadly involves the resistance shown, and
protection offered by the host organism against the
infectious diseases.
-The immune system consists of a complex network of
cells and their interactions .
-It is specific
-ally designed to eliminate infectious organisms from the
body .
-This is possible since the organism is capable of
distinguishing the self from non-self ,and eliminate non-
self.

4. HISTORY OF IMMUNOLOGY
-Metchnikoff [1845-1916]
Metchnikoff is the Russian zoologist. He discovered the importance
of cells in immunity and phagocytosis.
-Emil Von Behring [1854-1917]
the greatest support for humoral theory came from the studies of
behring ,a German bacteriologist.
In 1890 ,he showed that it was possible to provide an animal with
passive immunity against tetanus or lockjaw by injecting into it the
blood serum of another animal infected with tetanus.
-Alexander fleming [1881-1955]
Fleming a British bacteriologist received Nobel prize in 1945 for his
dicovery of penicillin.
He discovered the antibiotic lysozyme.

5. INNATE AND ACQUIRD
IMMUNITY
Innate immunity-All living organisms are naturally gifted
with the resistance to certain infections from birth and
this natural defence mechanism is known as innate
immunity or native immunity or natural immunity.
It is also known as non –specific immunity
Acquired immunity- the restistance developed by man
during his life is known as acquired immunity or adeptive
immunity.

8. CELL OF THE IMMUNE
SYSTEM
Two types of lymphocytes namely B-cell and T-cell are critical for
the immune system. In addition, several accessory cells and
effector cells also participate.
A] B- lymphocytes - the site of development and maturation of B-
Cell occurs in bursa fabricus in birds ,and bone marrow in
mammals. During the course of immune response. B-cell mature
into plasma cell and secrete antibodies [immunoglobulins].
B-Lymphocytes are inimately associated
with humoral immunity.
B] T-Lymphocytes- the mononuclear , nongranular leucocyte that
matures in thymus and that brings about cell mediated immunity
is called T Lymphocyte.
The T lymphocytes are thymus dependent cell. They mature under
the influence of thymus hormones.
The Tlymphocytes have a large nucleus and a rim of cytoplasm.
They are highly concentrated in the blood and spleen.

10. TYPES OF T -CELLS
Ts cell [T-Suppressor cells]- Ts cells are a sub
population of t cells that suppress the activity of B cells
and other T cells. They are the regulatory T cells. They
inhibit antibody production by B cell . They suppress the
functions of the T killer cells and T helper cells.
T cytotoxic cells [Tc] or T Killer cells [Tk]- The T Killer
cells are a sub population of T Lymphocytes that kill
micro-organism or body’s own cells.
They are also called cytotoxic cells. They are represented
by Tc Or Tk.
The T Killer cells are effector cells.

12. T Helper cells –T helper cells- T helper cells are a sub
population of T lymphocytes that help B cells and other T
cells in immune responses. They are the regulator cells.
They help the B cells and T cells in multiple ways . T
helper cells are a sub population of T lymphocytes that
help B cells and other T cells in immune responses. They
are the regulator cells . They help the B cells and T cells
and in multiple ways.
The T helper cells are represented by T Helper.

13. ORGANS OF IMMUNE
SYSTEM
Primary lymphoid organ - primary lymphoid organs are
the major site of lymphopoiesis*. The thymus , the
Bursa of fabricius in birds and bone marrow in mammals
are the primary lymphoid organs.
Thymus- Thymus is a primary limphoia organ . In
mammals , the thymus is a pharyngeal derivation arising
from the epithelium of the 3rd and 4th pharyngeal
pouches at about the 6th week of gestation.
Bone marrow- bone marrow is a primary lymphoid
organ. It is a solt tissue within the cavities of bones . In
marrow is divisible into two regions , namely
1) vascular and adipose region
2) Haemopoietic region

14. Secondary lymphoid organ – The secondary lymphyoid
organs are concerned with immune reactions. In the
secondary lymphoid organs the lymphocytes are made
functional.
Lymph nodes – Lymph nodes are secondary lymphoid
organs. They are complex , cellular ,spherical or ovoid
structures present along the lymphatic ducts.
Spleen –Spleen is a secondary lymphoid organ . It is a
solid, encapsuleted organ located in the upper part of
the abdominal cavity behind the stomach and close to
the diapharagm.
Peyers patches- peyer’s patches are secondary
lymphoid tissues. They are MALT. (mucosa associated
lymphoid tissue) . They are collection of lymphoid
nodules packed together to from oblong elevation of
the mucous memberane of the small intestine.

16. MALT- MALT is the mucosa associated Lymphoid tissue .
The muvosal layer of alimentary canal,respiratory and
urinogenital tracts is provided with dispersed groups of
lymphoid tissues known as MALT.
GALT – tissues are usually without a capsuie
(uncapsulated) . In human beings the peyer’s patches,
the tonsils and appendix are good examplesof lymphoid
tissues found in the mucosal layer of the alimentary
canal . Hence these tissues are also referred to as GALT
(Gut associated lymphoid tissue).