neutrophils, macrophage, dendritic cell, nk cell

1. CELLS OF
INNATE
IMMUNITY
DR/EMAN AHMED ABD-ALRAHMAN

2. 1)Cells of innate immunity
• Phagocytes: Neutrophils and Monocytes/
Macrophages
• Dendritic Cells
• Mast Cells
• Innate Lymphoid Cells
• Natural Killer Cells
• Lymphocytes with Limited Diversity

4. CELLS OF INNATE
IMMUNE RESPONSE
1) Natural Killer (NK) Cells
These are large granular lymphocytes .They
comprise 5-10% of the peripheral lymphocytes.
Surface markers
 CD16 +ve, CD56 +ve.
 CD16 is a receptor for Fc of IgG, which help
NK to bind to antibody coated cells and kill
these cells.
 CD56 is a cell adhesion molecule having a role
in cell–cell adhesion.

5. Functions:
 They have spontaneous non-specific cytotoxic
activity on virus infected cells, and intracellular
bacteria, so NK cells eliminate reservoirs of
infection.
 They kill viral infected cells very early in
infection before antigen-specific CTLs are
activated.
 They kill tumour cells and graft cells
 They secrete IFN- that activates macrophages
to destroy phagocytosed microbes.
CELLS OF INNATE
IMMUNE RESPONSE

6. Mechanism of NK mediated
cytolysis:
 NK cells are activated and
expanded by cytokines of innate
immunity IL-12, IL-15 and IFN
and.
 NK cells have granules that
contain perforins which create
pores in target cell membranes,
and granzymes, which enter
through the pores and induce
apoptosis of target cells.
CELLS OF INNATE
IMMUNE RESPONSE

7. NK cells mediated cytolysis differs from
CTLs in the following:
 They are non-specific i.e. one NK cell can kill many
different foreign cells.
 They act spontaneously without prior recognition or
activation.
 They do not require antigen presentation by MHC
i.e. not MHC restricted.
 They destroy cells coated with antibodies i.e.
antibody dependent cellular cytotoxicity (ADCC).
CELLS OF INNATE
IMMUNE RESPONSE

8. Regulation of NK mediated cytolysis:
NK cell activation and recognition of infected cells is
regulated by a combination of activation receptors and killer
inhibitory receptors (KIR) on NK cells.
a) KIR bind to self class 1 MHC on normal cells and inhibit
NK cells killing action; that is why NK cells do not kill normal
host cells. They kill cells with reduced or lost expression of
MHC-I as virus infected cells and tumor cells.
b) At the same time, activating signals are induced by
binding of activating receptors to molecules that are
expressed on the surface of infected cells, thus the infected
cells are killed.
CELLS OF INNATE
IMMUNE RESPONSE

10. IL-2 activated NK cells are called LAK .These cells have
been used in cancer immunotherapy; however, they
have shown variable results in clinical trials to treat
metastatic cancer.
CELLS OF INNATE
IMMUNE RESPONSE

11. If a microorganism crosses an epithelial barrier and
begins to replicate in the tissues of the host, in most
cases, it is immediately recognized by resident
phagocytic cells.
The main classes of phagocytic cells in the innate
immune system are : macrophages
monocytes
Granulocytes
dendritic cells.
Macrophages are the major phagocyte population
resident in most normal tissues at homeostasis.
CELLS OF INNATE
IMMUNE RESPONSE

12. Origin of macrophage:
a) Progenitor cells that enter the tissues during embryonic
development(arise from either the fetal liver, the yolk
sac), and then self-renew at steady state during life
b) Circulating monocytes.
PHAGOCYTES

13. PHAGOCYTIC CELL
Name of cell Location
Dust cells/Alveolar macrophages alveoli of lungs
Histiocytes connective tissue
Kupffer cells liver
Microglia neural tissue
Epithelioid cells granulomas
Osteoclasts bone
Sinusoidal lining cells spleen
Giant cells Connective Tissue
Peritoneal macrophages Peritoneal cavity

14. MACROPHAGE
Surface markers:
 CD14 (the endotoxin receptor) is the best marker for
macrophages.
 Other markers include receptors for Fc of IgG,
complement receptors CR1 and CR3 and receptor for
INFγ.
 MHC-II and I, and B7 are expressed on activated
macrophages

15. MACROPHAGE
Functions
I. Phagocytosis:
The process of phagocytosis includes the following stages:
a. Chemotaxis, Migration and Attachment:
If an infectious agent breaches an epithelium and enters the
sub-epithelial tissues, the resident macrophages are
attracted to the site of inflammation by chemotactic
substances liberated from microbes and damaged tissues.
These include bacterial endotoxins (LPS), serum complement
C5a, IL-8 (chemokine) and leukotrienes.

16.  The macrophages respond by producing soluble proteins
(cytokines) e.g. TNF- and IL-1. These activate the
endothelial cells of the nearby venules to produce
adhesion molecules and chemokines, which mediate the
migration of leucocytes and monocytes from the blood
through the endothelial wall of blood vessels to the
tissues (i.e. diapedesis).
 The phagocytes have many receptors (e.g. mannose
receptors, scavenger receptors and Toll-like receptors)
on their surface through which they attach non-
specifically to microbes.
 Attachment and ingestion are greatly enhanced if the
organism is coated by its specific antibody, by activated
complement C3b or by antibody and C3b (opsonins) and
the process is called opsonization.

17. b. Ingestion:
 The phagocytes proceed to engulf the organism by
extending pseudopods around it. These fuse and
the organism is included into a vacuole called
phagosome.
 Lysosomal granules then fuse with the phagosome,
forming the phagolysosome.
 This is followed by digestion of microorganisms.

18. c. Intracellular killing or digestion:
This can occur through:
1)The oxygen-dependent killing system in which
oxygen is converted to superoxide anion, hydrogen
peroxide, activated oxygen and hydroxyl radicals
(oxygen burst, respiratory brust). Myeloperoxidase
produces hypochlorite from H2O2. Nitric oxide is also
produced. All are powerful microbicidal agents.

19. 2)The oxygen-independent killing which is the result of
lysozomal granules content which include; lysozyme,
lactoferrin, a group of cationic proteins (defensins), and a
variety of hydrolytic and proteolytic enzymes.
phagocytosis is carried by:
b) Polymrophonuclear leucocytes (mainly neutrophiles)
b) Mononuclear phagocytes (monocytes in the blood and
macrophages in the tissues).

20. II. Opsonization:
Macrophages have surface C3b and Fc receptors that
interact with Fc portion of IgG thereby enhancing the
uptake of organisms coated with antibody alone or antibody
and complement.
III. Secretory function:
They produce IL-1, IL-6, IL-12, IL-15, TNF-, IFN, and
chemokine IL-8.
They secrete prostaglandins and synthesize complement
components.

21. VI. Initiation of adaptive immune response:
Macrophages are important APCs. They ingest foreign
material, process it, and fragments of antigen are
presented on its surface (in association with MHC
molecules) for interaction with T cells.
V. Antibody dependent cellular cytotoxicity (ADCC):
Macrophages may also kill antibody coated infected
cells or tumor cells (ADCC) through the release of lytic
enzymes at the site of Fc-mediated contact and
secretion of TNF-α resulting in cytotoxicity

22. DENDRITIC CELLS
 The name dendritic describes their many long narrow
processes which make them very efficient at making contact
with foreign material.
 Dendritic cells are primarily located under the skin and
mucosa of most organs where they capture foreign antigens
and transport these antigens to local lymph nodes, where
they present antigen to naive helper T cells.

23. Origin and maturation:
DCs can originate from both lymphoid and myeloid lineages.
a. Myeloid lineage “classical” DCs: originate from
1. CD34+ myeloid progenitor cells (CD14 negative) can mature to
what is called a Langerhans DC, in the presence of TGF-β.
DENDRITIC CELLS
Langerhans DC are:
Mainly present in the skin and mucosa of upper GIT and GUT.
Capable of activating naïve T cells (but not B cells) as they capture
antigens, migrate to lymphoid tissues and present antigen to T
cells.

24. 2. Monocytes in the presence of GM-CSF and TNFα ±
IL-4. When this type of DC matures, it is known as an
interstitial DC (CD14+).
DENDRITIC CELLS
Interstitial (tissue) DCs are:
• Able to activate naïve CD4 and CD8 T cells.
• Can induce differentiation of naïve B cells to antibody
secreting plasma cells.
• Migrate to the lymphoid follicles (lymphoid tissue
associated DCs) and become follicular DCs or to mucous
membranes of the GIT, respiratory tact...etc. (i.e. mucosal
associated DCs).

25. b. Lymphoid lineage DCs (Plasmacytoid DCs):
The DC subset that originates from CD34+ cells committed to the
lymphoid lineage are CD11c- and are driven to become DCs by IL-
3.
They have the capacity to produce IFN-α and reside in the T cell
compartment of lymphoid tissues.
Surface markers:
 A single cell surface marker exclusively expressed on DCs has
not yet been identified. However they express:
 Large amounts of class II MHC antigens.
 Variety of adhesion molecules including CD11a (LFA-1),
CD11c, CD54 (ICAM-1), CD102 (ICAM-2), CD58 (LFA-3), and
CD50(ICAM-3).
DENDRITIC CELLS

26.  Co-stimulatory molecules including CD80 (B7.1),
and CD86 (B7.2), which are up-regulated during
DC activation. CD86 tends to be a marker of
early DC maturation, while CD80 only appears in
mature DC.
DENDRITIC CELLS

27. Functions:
DCs are the most efficient APCs. They are the main
inducers of the primary immune response, presenting
antigen to and activating naive T cells in the recognition
phase. They perform the following functions:
a. T cell activation:
The most prominent role for DCs is to process and present antigen to
activate both CD4+ and CD8+ T cells. Only DCs are capable of activating
naïve T cells.
Immature DCs originate in the bone marrow and migrate throughout the
body where they remain dormant waiting to interact with invading
pathogens or other foreign bodies (resident DCs).
At this point, DC matures and functions to capture antigen and process it
either by an exogenous (endosomal) pathway or by endogenous
(proteosomal) pathway.

28.  Processed antigen is presented in association with MHC-I to
activate CD8+ cells or in association with MHC-II to activate
CD4+ cells.
 Soluble antigens are carried directly to LN via afferent
lymphatics and blood vessels or drained indirectly by blood to
the spleen .
 DCs maintain on their cell surface co-stimulatory molecules
including members of the B7 family, TNF family and
intracellular adhesion molecules which are critical to the
activation of T cells and for the proper homing of DCs before
and after antigen capture.

29. b. Induction of immune tolerance:
DCs induce immune tolerance via:
* The central tolerance mechanism:
 DCs are found in abundance in the thymus, where newly produced T
cells are educated to become functional CD4+ T cells and CD8+ T
cells and undergo selection to eliminate cells active against ‘self’.
 Developing T cells are exposed to DCs loaded with self peptides.
 Low affinity reactive T cells are positively selected and allowed to
survive and reach the periphery.
 T cells that respond to DCs carrying self-peptides are destroyed in
the thymus by negative selection

30. * The peripheral tolerance mechanisms: DCs
contribute to peripheral tolerance via Inducing
apoptosis in self reactive T cells.
c. B cell stimulation/function:
DCs produce a number of cytokines and factors which are critical to
the activation and differentiation of B cells.
Follicular DCs (FDCs), which are found in germinal centers of lymph
nodes, appear to be important in the maintenance of B cell memory as
after the initial antibody response begins, the FDCs form numerous
complexes of antigen and antibody that act as reservoir of continued
stimulation for B cells.

31. DCs depend on cytokines to cross talk with other cells
of immune system:
•Their activation results in the production of pro-
inflammatory cytokines including type I INF and acute
phase cytokines such as TNF, IL-6 & IL-12.
•DCs are activated by variety of cytokines including IL-1,
TNF & type I INF.
Professional APCs are the dendritic cells,
macrophages, and B lymphocytes.

32. NEUTROPHILS
* Neutrophil granulocytes are the most abundant type of white
blood cells in mammals and form an essential part of the innate
immune system.
* They form part of the polymorphonuclear cell family (PMNs)
together with basophils and eosinophils.
*Neutrophils have a variety of specific receptors including
complement receptors,
 Cytokine receptors for interleukins and interferon gamma
(IFN-gamma).
 Receptors for chemokines, receptors to detect and adhere to
endothelium.
 Receptors for leptins and proteins.
 Fc receptors for opsonin.

33. NEUTROPHILS

34. Functions:
Neutrophils are one of the first-responders of inflammatory cells to
migrate towards the site of inflammation.
They migrate through the blood vessels, then through interstitial
tissue, following chemical signals such as Interleukin-8 (IL-8), C5a
and Leukotriene B4 in a process called chemotaxis.
NEUTROPHILS

35. They function mainly in innate immune response against
invading pathogens via:
a. Recruitment and activation of other cells of the immune
system: Neutrophils express and release cytokines, which in
turn amplify inflammatory reactions by several other cell
types.
b. Phagocytosis (ingestion):
Neutrophils are phagocytes, capable of ingesting
microorganisms or particles.
NEUTROPHILS

36. Granule type Protein
• Primary granules (azurophilic
granules)
• myeloperoxidase,
bactericidal/permeability-
increasing protein (BPI),
Defensins, and the serine
proteases neutrophil elastase
and cathepsin G.
• Secondary granules (specific
granules)
• Lactoferrin and Cathelicidin
• Tertiary granules • Cathepsin and gelatinase
c. Release of soluble anti-microbials:
Neutrophils contain three types of granules that release
different proteins by a process called degranulation:
NEUTROPHILS

37. d. Generation of neutrophil extracellular traps (NETs):
Activation of neutrophils causes the release of web-like
structures composed of chromatin and serine
proteases that trap and kill microbes extracellularly
independent of phagocytic uptake. Also NETs serve as
a physical barrier that prevents further spread of
pathogens.
e. ADCC.
NEUTROPHILS

38. BASOPHILES
 They originate from bone marrow precursors expressing
the CD34 molecule and leave the bone marrow already
mature.
 They contain large basophilic granules that contain many
proteins and mediators as histamine, heparin and
chemotactic factors for eosinophiles and neutrophiles.
Functions:
1.Basophils contain anticoagulant heparin, which prevents blood
from clotting too quickly.
2.They contain the vasodilator histamine, which promotes blood
flow to tissues.
3.They play a role in both parasitic infections and allergies.
Basophils have protein receptors on their cell surface that bind
IgE.

39. EOSINOPHILS
They are granulocytes that develop in the bone marrow
before migrating into blood.
They are present in the circulation and tissues specially
lower GIT and GUT.
Eosinophilic granules are present in the cytoplasm, which
contain many chemical mediators and proteins such as
histamines, eosinophil peroxidase, ribonuclease (RNase),
deoxyribonucleases, lipase, plasminogen, and major basic
protein.
These mediators are released by a process called
degranulation following activation of the eosinophil.

40. EOSINOPHILS
Functions:
Eosinophils play a role in:
 Fighting viral infections, which is evident from the
abundance of RNases they contain within their granules.
 Fibrin removal during inflammation.
 Eosinophils along with basophils and mast cells, are
important mediators of allergic responses and asthma
pathogenesis and are associated with disease severity.
 Fighting helminth colonization and may be slightly
elevated in the presence of certain parasites.

41. The best surface markers for detection of immune cells are:
CD3→T cells
CD14→ monocytes & macrophges
CD19→B cells, CD56→natural killer cells and
CD66b→granulocytes.

42. MAST CELLS
They are resident cells of several types of tissues and contain
many granules rich in histamine and heparin. Although best known
for their role in allergy and anaphylaxis, mast cells play an
important protective role as well, being intimately involved in
wound healing and defense against pathogens.
Origin and maturation:
They originate from bone marrow precursors (stimulated by IL-3
and stem cell factor SCF) expressing CD34 molecules leaving the
BM as immature cells that mature in the tissues.

43. MAST CELLS
Types:
Two types of mast cells are recognized:
Connective tissue mast cells.
Mucosal mast cells
Sites:
Mast cells are present in most tissues characteristically
surrounding blood vessels and nerves, and are especially
prominent near the boundaries between the outside world
and the internal milieu, such as the skin, mucosa of the lungs
and digestive tract, as well as in the mouth, conjunctiva and
nose.

44. MAST CELLS
Mast cell mediators:
1- Preformed mediators (from the granules):
a) Histamine (2-5 pg / cell).
b) proteoglycans, mainly heparin
(active as anticoagulant).
c) Serine proteases, such as tryptase.
d) Serotonin.

45. MAST CELLS
Functions:
1- Allergic diseases:
Many forms of cutaneous and mucosal allergy are mediated
for a large part by mast cells; they play a central role in
asthma, eczema, itch (from various causes) and allergic
rhinitis and allergic conjunctivitis. Antihistamine drugs act by
blocking the action of histamine on nerve endings.

46. MAST CELLS
2- Anaphylaxis:
In anaphylaxis wide degranulation of mast cells leads to
vasodilation and, if severe symptoms of life-threatening shock
occur.
3- Autoimmunity:
Mast cells are implicated in the pathology associated with the
autoimmune disorders as rheumatoid arthritis and multiple
sclerosis. They have been shown to be involved in the
recruitment of inflammatory cells.
4- Reproductive disorders:
Mast cells are present within the endometrium, with increased
activation and release of mediators in endometriosis. In males,
mast cells are present in the testes and are increased in oligo-
and azoospermia, with mast cell mediators directly suppressing
sperm motility.

47. MAST CELLS
2- Newly formed mediators:
Thromboxane.
Prostaglandin D2.
Leukotriene C4.
Platelet-activating factor.
3- Cytokines:
Eosinophil chemotactic factor.
neutrophil chemotactic factor