Download the immune response

Immuno-Pharmacology
Dr. Dalia El Tanbouly
•
Immunopharmacology: study of drugs
that modulate immune response (↑ or ↓).
•
Immune system consists of:
– Organs:1ry(Thymus, bone marrow)
2ry (spleen, lymph nodes)
– Cell types: neutrophils, monocytes,
natural killer cells, etc.
– Molecules: complement component.
•
Communication among elements:
– Surface receptors
– Soluble molecules (cytokines).
Targets of Immune Response:
– Invading organisms.
– Growing neoplastic cells.
• Immune system must distinguish self from
non-self.
• Foreign substances that elicit a specific
immune response are called antigens.
Types of Immune Response:
Innate (natural):
• 1st line defense
• Non-specific.
Adaptive (acquired):
• Specific.
• Have memory.
• Subdivided into:
– Humoral (B-lymphocytes).
– Cellular (T-lymphocytes).
Characteristics of Innate &
Acquired Immune Responses
Innate:
Acquired:
• Onset: Immediate.
• Onset: Days to weeks.
• Does not require priming. • Require priming.
• Effectors:
• Effectors:
Physical: skin and mucous
membranes.
Cellular: macrophages, neutrophils,
mast cells, natural killer cells, etc.
Biochemical: cytokines, lysozymes
and complement (cell lysis (MAC),
opsonization C3b, chemotaxis C5a)
Cellular:
– B-lymphocytes.
– T-lymphocytes.
• T helpers (CD4).
• T cytotoxic (CD8).
– Phagocytes (APC).
Biochemical:
cytokines, lysozymes, complement
and immunoglobulins
• Onset upon re-exposure: • Onset upon re-exposure:
the same.
quicker.
• Memory:
• Memory
Present
Absent
Cytokines
• Soluble small peptides used by the immune
system to communicate & influence cellular
functions.
• Involved in innate & adaptive immunity.
• Chemokines: low molecular weight cytokines act
as chemoattractants
e.g Interleukin-8 (IL-8), which induces neutrophils to leave the
bloodstream and enter into the surrounding tissue
Monocyte chemoattractant protein-1 (MCP-1) which induces
monocytes to leave the bloodstream and enter the surrounding
tissue to become tissue macrophages.
APC
Memory B-cells
TH
IL-2
IL-2
IL-2
TH1
TH1/TH2
IL-2, IL-4, IL-5,
INF-γ
IL-2, INF-γ, TNF-β
Activated
NK cell
Activated macrophages
IL-1, TNF-α
(pro inflammatory cytokines)
IL-12
IL-8
Ingestion and killing microbes
Damage cells
Remove cellular debris
Activated
Cytotoxic T
cell
Kill virus
infected cells ant
tumor cells
IgE
IgA
IgG
IgM
-Neutralization of microbes and toxins
-Opsonization of antigens for phacocytosis by
macrophages and neutrophils.
-Activation of classical pathway of complement (lysis)
-Antibody-dependent cellular cytotoxicity by NK cells.
Examples of some cytokines:
• IL-1 & TNF-α (pro inflammatory cytokines)
increase vascular permeability promoting inflammation.
• IL-2 (T cell growth factor): T- cell proliferation and
differentiation into effector and memory cells.
• IL-4 (B cell growth factor): TH2 derived growth factor,
essential for IgE production
• IFNs (α, β ): Possess antiviral effects.
• IFNγ: Macrophage activation, essential for IgG production,
possess antiviral effects.
• IL-12:
Produced
differentiation.
by
macrophage
promoting
TH1
Abnormal Immune Response:
• Abnormal impaired immune response
→ Immunodeficiency.
• Abnormal exaggerated immune
response:
 Hypersensitivity reactions.
 Autoimmune diseases.
Antibody - mediated
Type I: Atopy, Allergy, Anaphylactic HS,
immediate
Type II: Cytotoxic
Type III: Immune complex
Cell - mediated
Type VI:
DTH
(Atopy - Allergy – Anaphylactic - Immediate)
Mechanism
1st exposure
to allergen
2nd
exposure to
allergen
Abnormal
IgE
production
Cross linking of fcR
through membranebound IgE by
allergen
IgE fixed on the
surface of mast
cells or basophils
via fcR
(Sensitization)
Ca2+ influx
Ca2+ influx
Degranulation of mast/basophil cells
Release of stored (preformed) mediators
Histamine
+ Heparin + Proteolytic enzymes + ECF + Serotonin
Immediate phase response
Synthesis & release of:
• Arachidonic acid metabolites
Lipoxygenase
LTs
Cyclo-oxygenase
PGs - TX
Immediate Phase
Histamine
LTC4 / LTD4
Vasodilatation, Vascular permeability, transient
contraction of smooth muscle
Prolonged smooth muscle contraction
Bronchoconstriction -  Bronchial secretions
Mucosal edema
Histamine – Kinins Vasodilatation - PG
 Vascular permeability  edema
Proteasese
Tissue damage – inflammation
Cytokines ( TNFαIL-4), LTB4
Attraction of leucocytes (eosinophils & neutrophils )
The attracted eosinophils & neutrophils release
proteases & mediators
Late phase response
Clinical Manifestations
LOCAL
At the sites in which mast cells
accumulate
Main organ
affected
Skin
(contact)
Nose & Eyes
(contact)
Disease
Eczema - Urticaria
(hives)
Rhinitis, Conjunctivitis
(hay fever)
Lung
Allergic bronchial
(inhalation)
asthma
GIT
Allergic
(ingestioin) gastroenteropathy
SYSTEMIC
Anaphylaxis
Due to administration of
(as
by injection)  Release of
Severe life-threatening 
hypotension – airway
obstruction due to laryngeal
edema
(Ab mediated cytotoxicity)
Mechanisms
Generated by actions of antibodies usually IgG or IgM against
an epitope on host cell membrane or extracellular matrix .
which may be non self
molecules
Drug or microbial toxin (hapten) is
passively adsorbed onto cell
membrane
Changes these self structures
to be antigenic
Production of antibody (IgG
or IgM) that is directed
against it
OR a self molecules  Antibody-mediated AID
(Cytotoxic)
Mechanisms
The bound antibody stimulates the cell damage
by a number of effector mechanisms
Antibody-Dependent Cell-mediated Cytotoxicity
Antibody-Dependent Phagocytosis of target cell
Antibody-Dependent Complement Activation
Antibody-Dependent disruption of cellular function:
e.g.: Antibodies against cell surface receptor, which may be blocking or stimulating antibodies
Antibody-Dependent Cell-mediated Cytotoxicity
Antibody-Dependent Phagocytosis of target cell
Target
Cell
Phagocyte
FCR
Antibody-Dependent Complement Activation
RBC
RBC with drug
adsorbed on its surface
RBC
IgG
Ag/Ab reaction
Complement
activation
RBC
Hemolysis
Formation of MAC
C
(Cytotoxic)
Examples of Antibody-mediated AID
1.
Myasthenia gravis (autoantibodies against Ach
receptors in MEP).
2. Hashimoto’s thyroiditis (autoantibodies against
thyroid cells).
(Cytotoxic)
Examples of Drug-induced T2HSR
Examples:
• Penicillin – phenacetin – quinidine  adsorbed on RBC surface
hemolysis  Hemolytic anemia
• Quinine  adsorbed on platelet surface  platelet lysis 
thrombocytopenia
(Cytotoxic)
Example of Microbial induced T2HSR
Salmonella  lipopolysaccaride endotoxin  adsorbed
on RBC  hemolysis. (Hapten)
Streptococcus is rich in an antigen
IgG and IgM generated against
protein can cross-react with cardiac
of the heart  impair cardiac
reactivity)
called M protein.
streptococcus M
tissues and valves
functions (cross
(Immune Complex)
Mechanism
Production of antibody ( IgM, IgG) that is directed against
circulating in
or in
Self molecule
Antibodymediated AID
Non-self molecule
(antigen-antibody complexes) that circulate in
the blood
high pressure vessels (e.g. renal glomeruli – synovium).
 release of mediators,
ROS,
lysosomal
enzymes

Inflammation (VASCULITIS) 
Damage to the vessel wall + VD &
increased vascular permeability +
( microthrombi)
 release histamine  vasodilation,
increased Vascular permeability
(VASCULITIS)
(Immune Complex)
For antigen that is circulating in the blood:
Exogenous
Post Streptococcal Glomerulonephritis
Streptococcal cell wall antigens
immune comlplex
Nephritis
Endogenous (AID)
Rheumatiod arthritis
caused by deposition of immune complexes in joints. The IgG in the immune
complexes can become an antigen, stimulating the production of IgM against the
bound IgG. The anti-IgG IgM is also termed the rheumatoid factor
extensive damage to bone and cartilage and joint
dysfunction. cartilage and joint dysfunction
Systemic lupus erythematosus (SLE)
Arises from autoantibodies formed against fragments of single or double stranded
DNA and some chromosomal proteins (e.g. histones). Because these molecules are
widespread throughout the body, the inflammation is broadly distributed
Nephritis Nephritis, Skin lesions and Arthritis
(Delayed)
Mechanism
1. CD4+ (Th-1)-mediated:
1.
CD4+ (Th-1) cells interact with processed presented antigen 
Release of cytokines (e.g. IFN - TNFβ)  Activation of
macrophages
2.
Activated macrophages release:
• Lytic enzymes, inflammatory cytokines (e.g. TNFα, IL-1) 
Inflammatory response & Tissue injury.
• IL-12  Stimulates Th-1 to release more IFN - TNFβ 
Continual cycle
Chronic exposure to the antigen  Excessive accumulation & activation
of macrophages  Giant cells  Epithelioid cells  Granuloma
formation (The attempt of the body to isolate a site of persistent
stimulus)
(Delayed)
Mechanism
2. CD8+ (CTL)-mediated:
CD8+ cells interact with processed presented antigen  Release of killing
enzymes  cytolysis & inflammatory responses.
Examples
•
Chronic infectious diseases:
(bacterial – viral – protozoal - fungal).
•
Leprosy
Contact dermatitis:
(haptens + skin proteins  immunogen).
•
•
Graft rejection.
AID: Multiple sclerosis (Myelin basic
protein) and Crohn's disease
Graft rejection
Contact
dermatitis
When the body produces immune response
against itself (i.e. loss of self-tolerance)
Mechanisms
1. Molecular mimicry
2. Activation of anergized auto-reactive T-cells
3. Loss of suppression of auto-reactive T-cells
4. Alteration of normal proteins
5. Release of sequestered antigens
1. Molecular mimicry
Some pathogens (bacteria or virus) have
epitopes that close similar to normal protein in
host tissue
Cross-reactivity
Infection is frequently associated with
development of autoimmunity…Why?
1. Molecular mimicry
Rheumatic fever
following Streptococcus pyogenes infection
Molecular mimicry between M protein of S. pyogenes &
the myosin of cardiac muscle & to some degree with
molecules on joints & kidneys.
 Antibodies against M proteins cross-react with myosin
in myocardium & joint tissue  Rheumatic fever.
2. Activation of anergized auto-reactive T-cell
Macrophages that are activated by infection
generate elevated levels of cytokines that may
activate anergized auto-reactive T-cell
Infection is frequently associated with
development of autoimmunity…Why?
3. Loss of suppression of auto-reactive T cells
Tolerance to self protein can be induced by
regulatory (suppressor) cells which diminish the
activity of possible auto-reactive T cells.
Decrease in no. of regulatory cells (as happen
with age)  Increases the risk of activation of
auto-reactive T cells  Autoimmunity.
4. Alteration of normal proteins
Neoantigens
Self Proteins
OR
Formation of neoantigen to immune system
 elicit immune responses
Hapten
Small molecule that stimulates the production of antibody molecules only when
conjugated to a larger molecule, called a carrier molecule.
e.g. drug-induced hemolytic anemia. Drugs capable of causing hemolytic anemia
include: penicillin, cephalosporins, sulfonamide, quinine
5. Release of sequestered antigens
Some self-molecules are normally sequestered (hidden)
from immune system by specialized anatomic structure:
• Certain tissues (sperm, lens).
Damage by Infection-Chemical-Radiation….
Release or exposure of the hidden self-molecules to immune
system & elicit immune responses.
Classifications
Organ-specific
ONE organ is subjected to
immunological attack
Crohn’s disease (intestine)
Hashimoto’s thyroiditis
Graves disease
T1DM (insulin-dependant)
Non-organ-specific
MORE than one organ is
subjected to immunological
attack
(i.e. systemic or diffuse)
SLE
Rheumatoid arthritis
Classifications
Humoral-associated
autoimmune disease
Pernicious anemia
Myasthenia gravis
Hashimoto’s thyroiditis
Graves disease
Systemic lupus erythematosus
N.B
Cell mediatedautoimmune disease
Insulin dependent diabetes mellitus
Crohn’s disease
Multiple sclerosis
Rheumatiod arthritis provides an example of
autoimmune disease that involves both humoral and cellmediated injury
Immunosuppressive Drugs
Therapeutic Uses
Used to  the immune response in
Autoimmune diseases
Transplantation
Immunosuppressive Drugs
Common Adverse Effects
Nonspecifically suppress the entire
immune system   risks of
Infections
Cancers
Immunosuppressive Drugs
Drug Classes
1. Glucocorticoids
2. Calcineurin inhibitors
3. Antiproliferative/antimetabolites
4. Antibodies/Fusion proteins
e.g. Cyclosporin(CsA) - Tacrolimus (TAC)
What is calcineurin?
It is a cytoplasmic phosphatase enzyme
involved in antigen-triggered synthesis of IL-2
(& IL-2R & other cytokines as IL-3, IFN-)
T cells growth and differentiation.
What is calcineurin?
DAG
PLC
PIP2
Ag
TCR
IP3
 PKC
 [Ca2+]
IL-2
 Calcineurin
PO4
NFAT
c
NFAT
n
NFAT
c
NFAT
c
IL-2 gene
Mechanism of action
inactive
active
Phosphorylated
NFAT (Nuclear
Factor of
Activated T
Lymphocytes)
Calcineurin
(phosphatase)
Dephosphorylated
NFAT
(-)
Cyclosporin
(+)
NFAT-GENE
complex
immunophilins
cyclophilin
Nucleus
FKBP-12
Tacrolimus
(+)
↑ IL-2 synthesis
Prototypic T-cells growth
and differentiation factor
DAG
PLC
PIP2
TCR
IP3
 PKC

[Ca2+]
Calcineurin
PO4
NFAT
c
NFAT
c
NFAT
n
IL-2 gene
Immunophillin Calcineurin
Inhibitor
Cyclosporine - Tacrolimus
Adverse Effects
 Nephrotoxicity (major)
 Hepatotoxicity
 Renal & Liver functions should be periodically
monitored
 Neurotoxicity (tremor, hallucinations, seizures).
 Hyperglycemia & diabetes
Cyclosporine - Tacrolimus
Adverse Effects
 Hypertension
 Hyperkalemia  avoid use of K-sparing diuretics.
 Anaphylactoid reactions
 Hirsutism
 Gum hyperplasia
 Hypercholesterolemia
 Hyperuricemia
CsA
TAC
1x
100x
Higher dose
required
Lower dose
required 
SE of GCs
Nephrotoxicity
+
++
Blood glucose
Glucose intolerance
DM
Hirsutism
+
-
Gum hyperplasia
+
-
Hypercholesterolemia
+
-
Hyperuricemia
+
-
Potency
GC co-administration
Cyclosporine - Tacrolimus
Drug Interactions
Co-administration of NSAIDs and any drug that causes nephrotoxicity
  nephrotoxicity
Cyclosporine + tacrolimus
  nephrotoxicity (Wait for at least 24h if switching from cyclosporine
to tacrolimus).
Calcineurin inhibitors especially tacrolimus + glucocorticoids   risk of
diabetes.
mTOR
inhibitors
Purine
synthesis
inhibitors
Sirolimus (Rapamycin)
Azathioprine
Everolimus
Mycophenolate mofetil
What is mTOR?
mTOR: mammalian Target Of Rapamycin
A key protein kinase enzyme responsible for
cell-cycle progression  Cell proliferation
IL-2
IL-2R
Immunophillin
mTOR
Proliferation
mTORI
Sirolimus - Everolimus
Mechanism of action
S
Sirolimus
immunophilins
FKBP-12
(-)
mTOR
G
1
Blocks cell-cycle progression induced by IL-2
& other T-cell growth factors.
(Inhibits the cellular response to IL-2)
Sirolimus - Everolimus
Adverse Effects
 Hypercholesterolemia (may require ttt)
 Myelosuppression
anemia, leukopenia, thrombocytopenia
 Fever, delayed wound healing, & GIT
effects.
 An additional adverse effect noted with
everolimus is angioedema
Sirolimus - Everolimus
Drug Interactions
Cyclosporine + sirolimus
Sirolimus   cyclosporine-induced nephrotoxicity.
Cyclosporine  sirolimus-induced hyperlipidemia
myelosuppression.
(Administration of two drugs should be separated by time).
&
Azathioprine
Mechanism of action
Azathioprine  6-mercaptopurine
 de novo purine synthesis
↓ DNA synthesis (S-phase)
 lymphocyte proliferation.
Azathioprine
Adverse Effects
 Myelosuppression 
leukopenia (common),
thrombocytopenia (less common),
&/or anemia (uncommon).
 Hepatotoxicity (mild)
 Alopecia, skin eruptions
 GIT toxicity (N,V)
 Pancreatitis
Azathioprine
Drug Interactions
Azathioprine  6-MP
Xan Ox
6-thiouric acid  urine
+ Allopurinol  xanthine oxidase inhibitor   level of
azathioprine …SO…..
azathioprine dose must be
decreased or avoid these combination).
+ Myelosuppressive drugs   risk of myelosuppression
Mycophenolate mofetil
Mechanism of action
Mycophenolate mofetil (Prodrug)
Mycophenolic acid (MPA) (Active drug)
Selective, non-competitive, reversible inhibition for
inosine monophosphate dehydrogenase
 de novo guanine synthesis
 lymphocyte proliferation & function
Mycophenolate mofetil
Mechanism of action
B & T lymphocytes are highly dependent on de novo purine
biosynthesis pathway for cell proliferation, while other cell
types can generate purines through other pathways
MPA
lymphocyte proliferation &
functions
Adverse Effects: GIT effects, leukopenia and anemia
Genetically engineered protein molecules
1. Antibodies
2. Fusion proteins
Polyclonal
Against several
antigens on surface
of lymphocytes or
thymocytes
(CD3,CD4,CD8, TCR)
Example:
Antithymocyte globulin Antilymphocyte globulin
Monoclonal
Against specific
antigen on surface
of lymphocytes
Against specific
cytokine or
serum component
Nomenclature
Animal
Chimeric
Humanized
Human
…….omab
…….ximab
…….zumab
…….umab
…….amab
…….emab
More antigenic
less antigenic
Mechanism of action
Against surface antigens
on lymphocyte
Lymphocyte
cytotoxicity
(complement-mediated
and cell-mediated)
Lymphocyte
function block
Against cytokine
or serum
components
Block function
of cytokine or
serum
component
Polyclonal
1. Antithymocyte globulin:
• Source: IgG from serum of rabbits
immunized with human thymocytes.
• Mechanism:
direct cytotoxicity to
circulating lymphocytes ➙ by direct
cytotoxicity (both complement and cellmediated) and block lymphocyte function
Adverse effects:
Fever, chills, headache, tremor, NVD, generalized weakness &
pain, skin reactions, cardiorespiratory, CNS disorders.
To minimize this:
a. Premedication è GCs, acetaminophen and antihistaminics to avoid allergy.
b. Administration by slow infusion (over 4 to 6 hours) into
large diameter vessel.
Anaphylaxis reaction
Serum sickness
Hematological complications (leukopenia and
thrombocytopenia).
Monoclonal
Against antigen on surface of lymphocytes
1. Muromonab-CD3:
Source: mouse monoclonal antibodies.
• Mechanism: Binding to the CD3 protein
results in a disruption of T-lymphocyte
function, because access of antigen to the
recognition site is blocked.
• Depletion of lymphocytes due to direct
cytotoxicity.
Adverse Effects
may follow the first dose as Initial binding of muromonab-CD3 to the
antigen transiently activates the T cell

cytokine release
(cytokine storm ) 
Toxicity
• The symptoms can range from a mild, flu-like illness to a lifethreatening, shock-like reaction.
• The symptoms
(30 min after infusion) 
frequency & severity decrease with subsequent doses.
• To minimize such reactions:
 Pre-medication with corticosteroids, acetaminophen, &/or an
antihistaminic.
 Administration by slow infusion (over 4 to 6 hours) into large
diameter vessel.
2. IL-2 receptor antagonist
(Daclizumab and Basiliximab).
• Binds to IL-2 receptors → ↓ IL-2-induced T
lymphocytes activation.
• Basiliximab is about 10-fold more potent than
daclizumab
3. IL-1 receptor antagonist (Anakinra)
• it binds to the IL-1 receptors → preventing
actions of IL-1.
• Anakinra treatment leads to a modest reduction
in the signs and symptoms of moderately to
severely active rheumatoid arthritis
Monoclonal
Against cytokine
1. Anti-TNF reagents
(Infliximab, Adalimumab)
• Mechanism: Binds to TNF-α → prevent
binding of TNF-α to its receptor → inhibits its
pro-inflammatory effects
• used in rheumatoid arthritis.
Soluble human TNF- receptor
Fused to
Fc domain of human IgG
Binds to TNF-
Prevents interaction of TNF- with its receptors
APC
Destruction of T
lymphocytes
TH
Inhibit IL-2
synthesis
IL-2
Calcineurin inhibitors
Cyclosporine - Tacrolimus
Block IL-2
receptors
mTOR inhibitors
Sirolimus and everolimus
Block cytokine stimulated
cell proliferation
-
Azathioprine
Mycophenolate mofetil
Antithymocyte globulin
Muromonab
(Daclizumab-Basiliximab)
IL-2 R
Cell cycle progression
G1-S
Inhibit purine synthesis
-
T cell proliferation
Macrophage
Anti IL-1 receptor
Anakinra
-
IL-1, TNF-α
-
Chronic inflammatory tissue injury
Anti TNF-α
Infliximab,
Adalimumab
Etanercept