This document discusses acquired immunity and its types. It describes the roles of natural killer cells, T lymphocytes, and B lymphocytes in acquired immunity. There are two types of acquired immunity: active and passive. Acquired immunity can be humoral, mediated by antibodies and B cells, or cell-mediated, mediated by T cells. Humoral immunity defends against extracellular pathogens through antibody production and activation of the complement system. Cell-mediated immunity protects against intracellular pathogens and is carried out by T cell activation and attack. Cytokines regulate the immune response through various functions. Acquired immunity has applications in vaccination, transplantation, and treatment of immune disorders.

1. ACQUIRED
IMMUNITY
DR.SUNDARESAN
PATHOLOGY
LOYOLA COLLEGE

2. Specific Learning Objectives
 Types of acquired immunity.
 List the functions of natural killer cells.
 Describe the role of T and B lymphocytes
in acquired immunity
 List the types of T cells and their role in
acquired immunity
 Describe T cell and B cell interaction
 Compare and contrast innate and
acquired immunity

3. Immunity - Classification
 Innate Immunity
 Acquired Immunity

4. Acquired Immunity
 Active Acquired
Immunity.
 Passive Acquired
Immunity.

5. Immunity - Overview

6. Acquired Immunity - Types
ACQUIRED IMMUNITY –
Humoral Immunity / B –
Cell Mediated Immunity.
Cell – Mediated
Immunity / T – Cell
Mediated Immunity.

7. Humoral Immunity
 Mediated by antibodies
 Antibody mediated immunity/ B cell mediated immunity.
 Defense against extracellular bacterial pathogens and viruses.
 Immediate hypersensitivity reactions & Autoimmune
conditions.
 Primary humoral response – first response to a specific antigen.
 Secondary humoral response – subsequent response to the
same antigen.

8. Humoral Immunity
 Antigen processing
and presentation
 Recognition of
antigen by
lymphocytes.
 Lymphocyte
activation.
 Production of
antibodies
 Inactivation of
antigen/ effector
phase.

9. IgM
•1st response to antigen
•Effective in agglutination
•Can’t cross placenta
IgG
•Most common form
•Crosses blood vessels
•Crosses placenta (passive
immunity to fetus)
IgA
•Secreted from mucus membranes
•Prevents attachment of bacteria to
epithelial surface
•In colostrum
IgD
•B cell activation
•Can’t cross placenta
IgE
•Histamine
reactions and
allergies
Immunoglobulin Classes

10. Humoral Immunity –
Effector Phase
 Direct attack on
invading agents
 Agglutination
 Precipitation
 Neutralization
 Cytolysis
 Attack on the antigen
through complement
system.

11. Humoral
Immunity –
Complement
System Opsonisation
 Lysis
 Agglutination
 Neutralization
 Chemotaxis
 Activation of mast
cells and basophils
 Inflammatory effects.

12. Cell – Mediated Immunity
 Specific acquired immunity.
 Mediated by T lymphocytes & macrophages – T cell mediated
immunity.
 Protects against fungi, most viruses and intracellular bacteria.
 Graft versus host reaction, Delayed hypersensitivity reactions,
Autoimmune diseases and cancer.
 Primary cellular response – first response
 Secondary cellular response – subsequent response.

13. Cell-mediated Immunity
Antigen processing
and presentation
Recognition of
antigen by
lymphocytes.
Lymphocyte
differentiation.
Attack
phase/effector
phase.

14. Cell-Mediated
Immunity –
T
Lymphocytes

16. Regulation Of Immune
Response
 CYTOKINES – protein molecules
 Interleukins 1-13, TNF ,IF, TGF, CSF
 Autocrine & paracrine function
 Mediates inflammation
 Synthesis of prostaglandins
 Increase the number of neutrophils, CSF ,
non-specific resistance/immunity.

17. Applied Aspects
 Immunization
 Immunosuppression
 Autoimmune diseases
 Organ transplants
 Hypersensitivity reactions
 Immunodeficiency diseases.