The document summarizes the major cells of the immune system. It describes granulocytic cells like neutrophils, basophils, and eosinophils which protect against bacteria and parasites. It also discusses mast cells, dendritic cells, macrophages, monocytes, B lymphocytes, T lymphocytes, and natural killer cells. Each cell type has a distinct role in the innate and adaptive immune response such as phagocytosis, antigen presentation, and production of antibodies and cytokines. Understanding these immune cells is crucial for developing treatments and preventing disease.

1. CELLS OF IMMUNE SYSTEM
DEBAM BIKASH PANIGRAHI
APPLIED MICROBIOLOGY
M.SC. 2nd SEMESTER
AMB-13/2022
FAKIR MOHAN UNIVERSITY,
NUAPADHI, BALASORE-756020

2. Intro
• The immune system is a complex network of cells, tissues, and organs
that work together to protect the body from harmful pathogens, such
as bacteria, viruses, and parasites.
• At the core of this system are the cells of the immune system, which
include a variety of specialized cells that have different roles in
recognizing, attacking, and eliminating foreign invaders.
• These cells are produced in the bone marrow and mature in various
organs throughout the body, such as the thymus, spleen, and lymph
nodes.
• Understanding the different types and functions of immune cells is
crucial for understanding how the immune system works and how it
can be manipulated to fight diseases.

3. Cells of immune system

5. Granulocytic cells
These are characterized by granular nature of cytoplasm.
They have multi-lobed nuclei. They are classified on the
basis of cellular morphology and cytoplasmic-staining
characteristics
as:
• Neutrophils
• Basophils
• Eosinophils

7. Neutrophils
• Neutrophils represent between 55-70% of the white blood cell
population and guard the skin and mucous membrane.
• They protect against bacterial and fungal infection by sensing the site
of infection, migrating to it, and destroying the infectious organisms
by phagocytosis.
• Neutrophils derived from bone marrow and mature there.
• They can produce toxic substances such as perforins, which produce
pores in the plasma membrane, and granzymes, which enters the
pores and induce apoptosis (programmed cell death) in the target
cell.

8. Basophils
• Like neutrophils, basophils are formed and mature in the bone
marrow.
• Basophils circulate in small numbers in blood and have a life span of
only 1-2 days.
• They are cells with bilobed nuclei and granular cytoplasm.
• These granules contain histamine, a chemical that is well known for
its involvement in allergic reaction and inflammation.
• Basophils can be activated by bacteria, viruses, and parasites, all of
which they detect by using TLRs.

9. Eosinophils
• They are normally found in very small numbers in blood and it’s
number increase greatly in case of parasitic infection and in allergic
reactions.
• Eosinophils are primarily defence in parasitic infections, during which
they produce powerful toxic enzymes.
• These cells also modulate the inflammatory response and may be
involved in the detoxification of foreign substances.

10. Mast cells
• Mast cells are responsible for allergic reactions and response to
parasitic infection.
• They are found throughout the body but most commonly in tissues
that are exposed to external environment, such as mucous
membrane.
• Mast cells leave the bone marrow at immature form and differentiate
into mature cells when they arrive at tissues sites.
• Activated mast cells produce a variety of mediators.
• Mast cells can also recruit and activate dendritic cells.

11. Dendritic cells
• Dendritic cells participate in both innate (by phagocytosis) and
adaptive (by presenting antigens) immune responses, depending on
the local environment in which they are found, and form a vital link
between the two.
• They are called dendritic cells because they have long membranous
extensions that resembles dendrites of nerve fibre.
• They are continuously produced in the bone marrow and move from
the marrow to all tissues.
• Dendritic cells are strategically located in mucosal tissues associated
with routes of pathogen entry such as the oral, respiratory, and the
genital mucosae.

12. • In the skin, dendritic
cells are called
Langerhans cells located
in the lower layers of
epidermis.
• In the intestine dendritic
cells are found in the
Peyer’s patches .

13. Macrophages and Monocytes
• Monocytes are mononuclear white blood cells derived from stem
cells in the bone marrow circulate in the blood.
• Normally the number of monocytes in the circulating blood is quite
small.
• During an infection, however, this number increases markedly When
there is an infection, they are called to the site by chemotactic factors
released from damaged tissue and from neutrophils already joined in
battle at the site.
• Once monocytes reach the site, they begin to adhere to vessel walls
and migrate out into the tissues, where they differentiate into
macrophages .

14. • Macrophages are responsible for recognising, engulfing, and
destroying bacteria, fungi, and protozoans.
• They are also involved in removing tumour cells, virus-infected cells,
and normal cells that have undergone apoptosis.
• Equally importantly, macrophages function in wound healing, tissue
repair, and bone remodelling.
• They also function as antigen-presenting cells in adaptive immune
responses.

16. Types of
Macrophages
Location
Microglial cells Central Nervous
system
Kupffer cells Liver
Alveolar
Macrophages
Lungs
Histiocytes Connective tissue
Mesangial cells Kidney
Osteoclast cells Bones

17. Lymphoid cells
• Lymphocytes constitute 20%–40% of the body’s white blood cells and
99% of the cells in the lymph. These lymphocytes continually circulate
in the blood and lymph and are capable of migrating into the tissue
spaces and lymphoid.
• organs, thereby integrating the immune system to a high degree.
• The lymphocytes can be broadly subdivided into three populations:
• *B cells, *T cells, and *natural killer cells—on the basis of function
and cell-membrane components.

18. B Lymphocytes (B cells)
• Derived it’s letter designation from it’s site of maturation bone
marrow.
• Mature B cells display of membrane-bound immunoglobulin
(antibody) molecules, which serve as receptor for Ag .
• The binding of the Ag to the Ab causes the cell to divide rapidly; its
progeny differentiate into :
1. Effector cells called Plasma cells , which produce antibody and
present antigen to T cells.
2.Memory B cells, which have a longer life span than naive cells, and
responsible for immunological memory.

20. T Lymphocytes (T cells)
• It derive it litter designation from their site of maturation in the
thymus.
• During its maturation within the thymus, the T cell comes to express
on its membrane a unique Ag-binding molecule called the T-cell
receptor.
• TCR recognize Ag that is bound to cell membrane proteins called
major histocompatibility complex (MHC).
• Activated T cells come in 3 main classes: cytotoxic T cells kill infected
cells, helper T cells help activate B cells as well as other type of
immune cells, and regulatory T cells supress the immune system once
the antigen is reduced or gone.

22. Natural killer cells
• Natural killer cells (NK cells) are derived from different stem cells.
• They are lymphocyte cells and form a unique population of
lymphocytes found in peripheral tissues and in blood.
• They are normally seen as large granular cells that has no antigen
receptors.
• NK cells are involved in the innate immune response in two ways;
through target cell killing (apoptosis) and through the production of
cytokines (TNF, GM-CSF).
• Unlike all other cells involved in immune response, NK cells do not
use TLRs.

23. Conclusion
• In conclusion, the cells of the immune system play a crucial role in
protecting the body against invading pathogens and foreign
substances.
• These cells work together in a complex system to recognize and
destroy foreign invaders and to prevent the development of diseases.
• The immune system also has the ability to remember past infections
and to mount a more rapid response to similar infections in the
future.
• Understanding these cells and their mechanisms can help develop
more effective treatments and preventative measures for diseases.