Immunity

IMMUNITY
DR NILESH KATE
MBBS,MD.
DEPARTMENT OF
PHYSIOLOGY.

OBJECTIVE
 At the end of the class you shoud know
 Architecture of immune system
 Immunity
 Antigens
 Antibodies
 Immune response development
 Other immune mechanims

INTRODUCTION
 Definition
 Types
 Antigens
 Antibodies
 Immune system
Immune response
Immunomodulation
Immunoenhancement
Immunosuppression
Immunotolerance.
Autoimmunity
Hypersensitivity

ARCHITECTURE OF IMMUNE
SYSTEM
 Mononuclear Phagocytic system – also
called as Tissue Macrophage system (1960)
previously called Reticulo endothelial sytem.
 Lymphoid components – consists of
network of lymphoid organs, nodes & cells.

MONONUCLEAR PHAGOCYTIC
SYSTEM
Formation
-Monocytes from bone
marrow circulates for 3
days & then enters
tissue & becomes tissue
Macrophages.
Saturday, June 16, 2018

TISSUE MACROPHAGES
 LIVER – Kupffer cells
 Spleen
 Bone marrow- Littoral cells
 Lungs – Pulmonary alveolar
macrophages
 Connective tissue –
histiocytes
 Bones – osteoclasts
 CNS – Microglial cells.

SYSTEM
 Constituent
cells
Precursor cells
of monocytes
Promonocytes
monocytes

SYSTEM
Functions
1 Role in inflammation &
healing
2 Role in defence against
bacteria
3 Role in immune response
4 Role in removal of old RBC
5 Role in removal of old WBC
& platelets
6 Storage function.

LYMPHOID
COMPONENTS
Primary lymphoid
tissue
 Thymus – contains
Thymocytes
containing
thymocin.
 Role – education
of lymphocytes to
become T
lymphocytes.
 Effects of
thymectomy –
marked infection.

LYMPHOID
COMPONENTS
Primary lymphoid
tissue
 Bursa equivalent –
bone marrow
 Lymphocyes from
bone marrow
become B
Lymphocytes
 Form plasma cells &
antibodies.

PERIPHERAL
LYMPHOID ORGANS
 lymph nodes
 structure
 function
 spleen
 structure
 Function
 MALT (Mucosa
Associated
Lymphoid Tissue)

REVIEW

PHAGOCYTOSIS

PHAGOCYTOSIS
 Stages
 Margination
 Diapedesis
 Chemotaxis
 Peudopodia formation – engulfment
 Killing / degradation

ANTIGEN
 Definition
 Hapten
 Immunogenicity
 Antigen specificity
 Species specificity
 Isospecificity

HISTOCOMPATABILITY
ANTIGENS
 Major Histocompatability complex
(Chromosome 6-short arm) HLA Ag
 MHC Class I
 MHC Class II
 MHC Class III

CELL MEDIATED IMMUNITY
 Role of cellular immunity
 Intracellular bacteria– M.tuberculosis, M.leprae
 Viruses
 fungi
 Allograft rejection & graft versus host
reaction
 Delayed hypersensitivity & autoimmune

TYPES OF IMMUNE RESPONSE
 Primary
 Secondary

STAGES
 Antigen processing and presentation

RECOGNITION OF
ANTIGEN BY
LYMPHOCYTES

T-LYMPHOCYTES
DIFFERENTIATION (ACTIVATION)
CD8 types
CD4 types
TT co-operation
Memory cells

ATTACK PHASE
 Role of cytotoxic T-
cell
 Lysis through cytotoxic
substances
 Induction of Apoptois
 Perforin mediated killing

MEMORY CELLS

HUMORAL MEDIATED
IMMUNITY
 Role of humoral immunity
 Extracellular bacterial pathogens.
 Immediate hypersensitivity
 Autoimmune diseases.

STAGES
 Antigen processing and
presentation
 Recognition of antigens
by lymphocytes
 Lymphocyte activation
 Activation of T-lymphocytes.
 Activation of B-lymphocytes.
 Role of plasma cells
 Role of memory cells

 PRODUCTION OF
ANTIBODIES
 Theories of antibody
production
 Clonal selection theory
(Burne 1957)
 Inactivation or attack
phase
 Direct attack
 Complement system

COMPLEMENT SYSTEM
 Classical pathway.
 L - Lysis
 A - Agglutination
 N - Neutralization
 A – activation &
degranulation of
mast cells
 C - chemotaxis
 O- Opsoniozation.
 Alternate pathway.

COMPLEMENT SYSTEM

ANTIBODIES
 Structure
 Heavy Chain
 Light Chain

TYPES
 Immunoglobulins (Ig)
 Ig G
 Ig A
 Ig M
 Ig D
 Ig E

IMMUNOGLOBULINS
FEATURE IgG IgA IgM IgD IgE
H chain γ α μ δ ε
L chain Κ or λ Κ or λ Κ or λ Κ or λ Κ or λ
Mol wt
(kd)
150 160-385 900 180 190
Serum
conc
12 2 1.2 0.03 0.00004
Half life 21 6 5 3 2
Placental
T
Yes No No No No
Compleme
nt fixation
C A C N N
ROLE Body
fluids
Body
surface
Blood
stream
Not known Type 1
hypersens
itivity

OTHER IMMUNE MECHANISM
RELATED ASPECTS.
 Immune tolerance
 Immune modulation
 Autoimmunity
 Hypersensitivity
 Immunodeficiency diseases.

IMMUNE TOLERANCE
 Def – State of
unresponsiveness to
an antigen.
 Types.
 Natural – Non-
responsiveness to self
antigen.

IMMUNE TOLERANCE
 Acquired.
 General – Due to
impairment of
immune system.
 Specific – specific
antigen becomes
tolerogenic.

MECHANISM OF TOLERANCE
 Clonal deletion – clones
are selectively deleted.
 Clonal synergy – cones of
cells might remain but not
activated.
 Clonal Suppression –
Inhibited through active
suppression.

FACTORS INFLUENCING
INDUCTION OF TOLERANCE.
 Species –tolerance varies from species to species
 Immunological competency of the host.
 Antigen – Physical nature, Dose, Route of
administration.
 Age of the host.

TOLERANCE TO FOETUS.
 Factors
 Placenta
 Alpha fetoproteins –
immunosuppressive agents
 Progesterone
 Fetal T cells.

IMMUNE MODULATION
 Immune Enhancement – increase in response
in terms of Rate, Intensity, Duration
 Adjuvant – Non-specifically enhance immune
response to an antigen.

IMMUNE ENHANCEMENT
 Mechanism of action
 Alter distribution & persistence of antigens
 Stimulate lymphocyte number.
 Activate Macrophages.
 Types
 Incomplete
 Complete

IMMUNE SUPPRESSION
 Immune suppression – Reduction in
immunological response.
 Specific
 Non-specific.
 Immunosuppressive agents.
 Physical
 Chemical
 Biological.

PHYSICAL
 Irradiation
 Surgical
procedures.
 Thymectomy
 Splenectomy
 Thoracic duct
drainage.

CHEMICAL
 Corticosteroids.
 Impair maturation of activated cells
 Suppress production of antibodies
 Cyclosporins – Inhibit IL-2
 Cytotoxic drugs – Inhibit nucleic acid synthesis
& replication.

BIOLOGICAL.
 Antigen induced suppression – Desensitization
against allergen
 Antibody induced suppression – used in
pregnant mothers.
 Anti-lymphocytic serum.

AUTOIMMUNITY
 Mechanism
 Forbidden clones.
 Hidden antigen or
sequestrated antigens
 Neo antigens or altered
antigens
 Cross reacting antigens
– molecular mimicry
 Mutations
 Unbalanced activity of
Helper & suppressor T
cells.

AUTOIMMUNE DIEASES.
 Autoimmune anemia
 Thrombocytopenic purpura.
 Grave’s disease
 Hashimoto’s disease
 Insulin dependent diabetes mellitus.
 Rheumatoid arthritis.
 Rheumatic fever.

HYPERSENSITIVITY
Abnormal response which produces
physiological or histopathological
damage in the host

HYPERSENSITIVITY
 Type I – local
Anaphylaxis
 Systemic &
generalized
anaphylaxis.
 Mechanism –
Degranulation of mast
cells & basophils by
Ag-Ab complex.
 Type II – Immediate
reaction
 Examples –
Incompatible blood
transfusion,
Autoimmune
hemolytic anaemia,
Hemolytic disease of
newborn.

HYPERSENSITIVITY
 Type III (Immune
complex mediated) –
damage of the
complex deposited in
tissue.
 Type IV – Delayed.
 Tuberculin tests
 Contact dermatitis

IMMUNODEFICIENCY
DISEASES.
 Defect may be in the
 Lymphocyte & Natural killer cells
 Phagocytic cells
 Complement proteins.
 PRIMARY Immunodeficiency
 SECONDARY.

PRIMARY IMMUNODEFICIENCY
DISEASE.
 Humoral immune deficiency
 Cellular immunodeficiency.
 Combined
 Complement immunodeficiency.
 Phagocytic disorders.

SECONDARY
IMMUNODEFICIENCY DISEASE.
 AIDS – Acquired
immunodeficiency syndrome.
 Reduction in Helper T cells
 First detected in USA 1981
(India-1986)
 Spread of disease – sex
workers, drug addicts,
homosexual males &
unscreened blood transfusion.

AIDS – ACQUIRED
IMMUNODEFICIENCY SYNDROME.
 Transmission – 3 routes
 Parenteral
 Sexual
 Transplacental.
 Structure of HIV –
Retrovirus.
 Core – 2 single strands of
genomic RNA, enzyme
reverse transcriptase &
protein P-15

AIDS – ACQUIRED
 Virus Multiplication
– virus comes in
contact with T4
antigen – passes into
cell – genomic RNA
synthesizes copy DNA
with help of reverse
transcriptase.

AIDS – ACQUIRED
 Incubation period – 2-10
years
 Window period – 2-6
months (tests are negative)
 HIV positivity indicated by
 Presence of P24
 Antiviral antibodies
 Reduced T cells

AIDS – ACQUIRED
 Signs & symptoms –
mostly opportunistic
infections due to low
immunity
 HIV tests.
 screening tests - ELISA
 Supplement tests –
Wesrnblot essay
 Confirmatory tests – virus
isolation, p24 detection

AIDS – ACQUIRED
 Treatment – Triple
drug treatment.
 Protease inhibitor,
 Reverse transcriptase
inhibitor,
 Azidothymidines
 Interleukins
 Prevention
 Education
 Screening
 Ban on prostitution.
 Safer sex
 Use of disposable
instruments.

OBJECTIVE ………
 At the end of the class you shoud know
 Architecture of immune system
 Immunity
 Antigens
 Antibodies
 Immune response development
 Other immune mechanims

THANK YOU

Immunity

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