IMMUNOCHEMISTRY

Dr. Aga Syed SameerCSIR Lecturer (Demonstrator)

Department of Biochemistry,

Medical College,

Sher-I-Kashmir Institute of Medical Sciences,

Bemina, Srinagar, Kashmir, 190018. India.

Immunology:

“Janis Kuby”. WH FREE MAN BOOKS

Instant Notes in Immunology:

PM Lydyard. VIVA BOOKS.

REFERENCES

Immunity:

“Free from burden”. Ability of an organism to recognize

and defend itself against specific pathogens or

antigens.

Immune Response:

“Third line of defense”. Involves production of antibodies

and generation of specialized lymphocytes against

specific antigens.

Antigen:

Molecules from a pathogen or foreign organism that

“provoke a specific immune response”.

THE IMMUNE SYSTEM

THE IMMUNE SYSTEM

It forms the Third Line of Defense Against Infection

COMPONENTS

THE IMMUNE SYSTEM

COMPONENTS

THE IMMUNE SYSTEM

Bone Marrow:

Is the primary source of pluripotent stem cells.

It becomes active only in the last months of fetal

development.

Gives rise to all hematopoietic cells including

lymphocytes.

Major Organ for B cell maturation.

All lymphoid /precursor cells in turn migrate to thymus

for T cell maturation.

COMPONENTS

THE IMMUNE SYSTEM

Thymus:

Is the bilobed encapsulated organ located behind sternum;

above and in front of heart.

Is the major organ for T cell maturation & development.

It remains highly active during fetal stage (max) and then

atrophies at puberty.

It is comprised of cortical, medullary epithelial cells,

stromal cells, interdigitating cells and macrophages.

These accessory cells are important in the differentiation

of immigrating T cell precursors and their selection prior

to their migration to secondary lymphoid tissues.

COMPONENTS

THE IMMUNE SYSTEM

Spleen:

Is large, encapsulated bean shaped organ with spongy

interior; located on left side of body below diaphragm.

It plays a major role in mounting immune responses to

antigens in the blood stream.

Blood-borne antigens and lymphocytes are carried into

the spleen through the splenic artery.

The splenic red pulp consists of a network of sinusoids

populated by macrophages and numerous red blood cells

(erythrocytes) and few lymphocytes; it is the site where old

and defective red blood cells are destroyed and removed.

The splenic white pulp surrounds the branches of the

splenic artery, forming a periarteriolar lymphoid sheath

(PALS) populated mainly by T lymphocytes.

COMPONENTS

THE IMMUNE SYSTEM

Lymph Nodes:

They are small solid structures found at varying points

along the lymphatic system.

Possess an enveloping capsule beneath which is

subcapsular sinus, the cortex, a paracortical region and

a medulla.

The cortex contains follicles comprised mainly of B

cells and follicular dendritic cells.

The paracortical regions contains masses of T cells.

Primary function is to produce an immune response

against any microbe they trap.

Innate or Genetic Immunity:

Immunity an organism is born with. Genetically determined.

May be due to lack of receptors or other molecules required for infection. Innate human immunity to canine distemper.

Immunity of mice to poliovirus.

Acquired Immunity:

Immunity that an organism developsduring lifetime. Not genetically determined.

May be acquired naturally or artificially.

Development of immunity to measles in response to infection or vaccination.

TYPES OF IMMUNITY

Types of Acquired Immunity

I. Naturally Acquired Immunity: Obtained in the course of daily life.1. Naturally Acquired Active Immunity:

Antigens or pathogens enter body naturally.

Body generates an immune response to antigens.

Immunity may be lifelong (chickenpox or mumps) or temporary (influenza or intestinal infections).

2. Naturally Acquired Passive Immunity:

Antibodies pass from mother to fetus via placenta or breast feeding (colostrum).

No immune response to antigens.

Immunity is usually short-lived (weeks to months).

Protection until child’s immune system develops.

Types of Acquired Immunity

II. Artificially Acquired Immunity:

Obtained by receiving a vaccine or immune serum.1. Artificially Acquired Active Immunity:

Antigens are introduced in vaccines (immunization).

Body generates an immune response to antigens.

Immunity can be lifelong (oral polio vaccine) or temporary (tetanus toxoid).

2. Artificially Acquired Passive Immunity:

Preformed antibodies (antiserum) are introduced into body by injection. Snake antivenom injection from horses or rabbits.

Immunity is short lived (half life three weeks).

Host immune system does not respond to antigens.

Assignment

Find Out

Vaccination

Immunization

Innoculation

Serum: Fluid that remains after blood has clotted and cells

have been removed.

Antiserum: Serum containing antibodies to a specific

antigen(s). Obtained from injecting an animal (horse, rabbit,

goat) with antigen (snake venom, botulism or diphtheria toxin).

Serology: The study of reactions between antibodies and

antigens.

Gamma Globulins: Fraction of serum that contains most of

the antibodies.

Serum Sickness: Disease caused by multiple injections of

antiserum. Immune response to foreign proteins. May cause

fever, kidney problems, and joint pain. Rare today.

Duality of Immune System

I. Humoral (Antibody-Mediated) Immunity Involves production of antibodies against foreign

antigens.

Antibodies are produced by a subset of lymphocytes called B cells.

B cells that are stimulated will actively secrete antibodies and are called plasma cells.

Antibodies are found in extracellular fluids (blood plasma, lymph, mucus, etc.) and the surface of B cells.

Defense against bacteria, bacterial toxins, and viruses that circulate freely in body fluids, beforethey enter cells.

Also cause certain reactions against transplanted tissue.

ANTIBODIES ARE PRODUCED BY B

LYMPHOCYTES

ANTIBODIES ARE PROTEINS THAT RECOGNIZE

SPECIFIC ANTIGENS

Duality of Immune System

II. Cell Mediated Immunity Involves specialized set of lymphocytes called T cells

that recognize foreign antigens on the surface of

cells, organisms, or tissues:

Helper T cells

Cytotoxic T cells

T cells regulate proliferation and activity of other

cells of the immune system: B cells, macrophages,

neutrophils, etc.

Defense against:

Bacteria and viruses that are inside host cells and are

inaccessible to antibodies.

Fungi, protozoa, and helminths

Cancer cells

Transplanted tissue

CELL MEDIATED IMMUNITY IS CARRIED OUT BY

T LYMPHOCYTES

Antigens

Substances that can be recognized by the immunoglobulin receptor of B cells, or by the T cell receptor when complexed with MHC, are called antigens.

Although a substance that induces a specific immune response is usually called an antigen, it is more appropriately called an immunogen.

Antigenicity is the ability to combine specifically with the final products of the above responses (i.e., antibodies and/or cell-surface receptors). Although all molecules that have the property of immunogenicity also have the property of antigenicity, the reverse is not true.

Hapten: Small foreign molecule that is not antigenic. Must be coupled to a carrier molecule to be antigenic. Once antibodies are formed they will recognize hapten.

Antigens-Antibody Interactions

Immunoglobulins

Structure

Function

Secretion

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