IMMUNITY

Dr. Shaikh Mujeeb AhmedAssistant ProfessorAlMaarefa College

HMIM BLOCK 224

ObjectivesGeneral overview of the immune systemDifferent components of innate & acquired

immunity. Phases of immune response.

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What is Immunity ?

Immunity is the body’s ability to resist or eliminate potentially harmful foreign

materials or abnormal cells.

What are the types of immunity

• Innate (natural) immunity• Acquired (adaptive) immunity

What is meant by innate immunity ?

• These nonspecific responses are inherent (innate or built-in) defense mechanisms that nonselective defend against foreign or abnormal material of any type, even on initial exposure to it.

What is it includes?

• Barriers– Physical– Chemical

• Defensive cells– WBCs– Macrophages– Natural killer cells (NK)

• Chemical defenses– Complement system

Barriers

• Integumentary system• Mucus membrane & lysozyme

Cells

• Langerhans cells• Phagocytes• Natural killer cells• Basophils and mast cells

Chemicals

• Interferon• Complement system• inflammation

Interferon

• α, β, and γ interferon • By infected cells• Block viral reproduction

Innate ImmunityMechanism of Action of Interferon in Preventing Viral Replication

Complement System

Series of ~ 20 proteinsActivated by microorganismsWill coat the microorganisms

Adherence reactionsphagocytic cells have receptors for C3

Biological active fragmentsproduce reactive oxygen intermediates

Membrane lesionsActivate mast cells

Acquired (adaptive) immunity

• specific immune responses selectively targeted against a particular foreign material to which the body has already been exposed.

• The foreign material may be an antigen or a hapten

Immune Response Antigen• Antigen – “any substance when introduced

into the body stimulates the production of an antibody”– Bacteria, fungus, parasite– Viral particles– Other foreign material

• Pathogen – an Antigen which causes disease

Immune Response Antibodies

• Antibody – “a Y-shaped protein, found on the surface of B-Cells or free in the blood, that neutralize antigen by binding specifically to it”

• Also known as an Immunoglobulin

Antigen

Hapten

• Not antigenic by itself• When combines with protein it become an

antigen

Adaptive immunity

• Two types1. Active immunity – direct encounter with the

antigen.2. Passive immunity – without encounter with the

antigen Antibodies transferred from mother to the fetus. Immunization by injecting antibodies

Active immunity

• Cell mediated immunity (T cell immunity)• Antibody mediated (humoral/ B cell) immunity

T and B Lymphocytes

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Origins of B and T lymphocytes

After early childhood most new lymphocytes are derived from peripheral

lymphocyte colonies rather than from bone marrow

Bone Marrow

Pre-BCell

Pre-TCell T-Cell

T-supressor

T4-helper

B-Cell Plasma Cell

IgG IgA IgM IgD IgE

Interactions between T- and B-Cells

T8-ctotoxic

T- memory Cell

B- memory Cell

Phases of immune mechanism

• Initial phase– Entry of antigen and its contact with the specific

receptor on lymphocytic membrane.• Central phase– Cooperation among different subset of lymphocytes

that proliferate and differentiate to form T & B lymphocyte + memory cells

• Effector phase– Inactivation of antigen by sensitized T & B

lymphocytes

References

• Human physiology by Lauralee Sherwood, seventh edition

• Text book physiology by Guyton &Hall,11th edition

• Text book of physiology by Linda .s contanzo,third edition