Immunoglobulin and monoclonal antibodies
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Immunoglobulin and Monoclonal antibodies. Reported by Ganesh M.Sc.D endo student. What is immunoglobulin ?.

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Immunoglobulin and Monoclonal antibodies

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Immunoglobulin and monoclonal antibodies

Immunoglobulin and Monoclonal antibodies

Reported by

Ganesh

M.Sc.Dendo student


What is immunoglobulin

What is immunoglobulin ?

Immunoglobulin's are glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies. The immunoglobulins derive their name from the finding that they migrate with globular proteins when antibody-containing serum is placed in an electrical field


Immunoglobulin and monoclonal antibodies

Papain

Fc

Fab

Immunoglobulin Fragments Structure/Function Relationships

Fab

Ag binding

Valence = 1

Specificity determined by VH and VL

  • Fc ( crystallizable)

    • Effector functions


Immunoglobulin and monoclonal antibodies

Ag Binding

Complement Binding Site

Binding to Fc Receptors

Placental Transfer

Immunoglobulin Fragments Structure/Function Relationships


Immunoglobulin and monoclonal antibodies

IgM

Structure

IgM normally exists as a pentamer (19S immunoglobulin) but it can also exist as a monomer. In the pentameric form all heavy chains are identical and all light chains are identical. Thus, the valence is theoretically 10. IgM has an extra domain on the mu chain (CH4) and it has another protein covalently bound via a S-S bond called the J chain. This chain functions in polymerization of the molecule into a pentamer.


Igm properties

IgM Properties

a) IgM is the third most common serum Ig.

b) IgM is the first Ig to be made by the fetus and the first Ig to be made by a virgin B cells when it is stimulated by antigen.

c) As a consequence of its pentameric structure, IgM is a good complement fixing Ig. Thus, IgM antibodies are very efficient in leading to the lysis of microorganisms.


Igm properties1

IgM Properties

d) As a consequence of its structure, IgM is also a good agglutinating Ig . Thus, IgM antibodies are very good in clumping microorganisms for eventual elimination from the body.

e) IgM binds to some cells via Fc receptors.

f) B cell surface Ig


Immunoglobulin and monoclonal antibodies

Surface IgM exists as a monomer and lacks J chain but it has an extra 20 amino acids at the C-terminus to anchor it into the membrane. Cell surface IgM functions as a receptor for antigen on B cells.


Immunoglobulin and monoclonal antibodies

Surface IgM is non covalently associated with two additional proteins in the membrane of the B cell called Ig-alpha and Ig-beta. These additional proteins act as signal transducing molecules since the cytoplasmic tail of the Ig molecule itself is too short to transduce a signal.


Immunoglobulin and monoclonal antibodies

IgD


Igd properties

IgD Properties

  • IgDis found in low levels in serum; its role in serum uncertain.

    b) IgDis primarily found on B cell surfaces where it functions as a receptor for antigen. IgD on the surface of B cells has extra amino acids at C-terminal end for anchoring to the membrane. It also associates with the Ig-alpha and Ig-beta chains.

    c) IgDdoes not bind complement.


Ige structure

IgE structure


Ige properties

IgE Properties

a) IgE is the least common serum Ig since it binds very tightly to Fc receptors on basophils and mast cells even before interacting with antigen.

b) Involved in allergic reactions - As a consequence of its binding to basophils an mast cells, IgE is involved in allergic reactions. Binding of the allergen to the IgE on the cells results in the release of various pharmacological mediators that result in allergic symptoms.


Ige properties1

IgE Properties

c) IgE also plays a role in parasitic helminth diseases. Since serum IgE levels rise in parasitic diseases, measuring IgE levels is helpful in diagnosing parasitic infections. Eosinophils have Fc receptors for IgE and binding of eosinophils to IgE-coated helminths results in killing of the parasite.

d) IgE does not fix complement.


Clinical implications of human immunoglobulin classes

clinical implications of human immunoglobulin classes

IgM Increases (in adults) in:

a) Waldenström'smacroglobulinemiab) Trypanosomiasisc) Actinomycosisd) Carrión's disease (bartonellosis)e) Malariaf) Infectious mononucleosisg) Lupus erythematosush) Rheumatoid arthritisI) Dysgammaglobulinemia (certain cases)

Note: In the newborn, a level of IgM above 20 ng./dl is an indication of in utero stimulation of the immune system and stimulation by the rubella virus, the cytomegalovirus, syphilis, or toxoplasmosis.


Clinical implications of human immunoglobulin classes1

clinical implications of human immunoglobulin classes

IgM Decreases in

a) Agammaglobulinemiab) Lymphoproliferative disorders (certain cases)c) Lymphoid aplasiad) IgG and IgA myelomae) Dysgammaglobulinemiaf) Chronic lymphoblastic leukemia


Clinical implications of human immunoglobulin classes2

clinical implications of human immunoglobulin classes

IgD Increases in

a) Chronic infections

b) IgD myelomas


Clinical implications of human immunoglobulin classes3

clinical implications of human immunoglobulin classes

IgE Increases in

a) Atopic skin diseases such as eczemab) Hay feverc) Asthmad) Anaphylactic shocke) IgE-myeloma


Clinical implications of human immunoglobulin classes4

clinical implications of human immunoglobulin classes

IgE Decreases in

a) Congenital agammaglobulinemia

b) Hypogammaglobulinemia due to faulty metabolism or synthesis of immunoglobulins


Immunoglobulin and monoclonal antibodies

Monoclonal antibodies are antibodies that are identical because they were produced by one type of immune cell, all clones of a single parent cell

Polyclonal antibodies are antibodies that are derived from different cell lines

Epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune systemspecifically by antibodies, B cells, or T cells.


Immunoglobulin and monoclonal antibodies

In 1975, Georges Kohler and CesarMilstein first fused lymphocytes to produce a cell line which was both immortal and a producer of specific antibodies. The two scientists were awarded the Nobel Prize for Medicine in 1984for the development of this "hybridoma."The value of hybridomas to the field was not truly appreciated until about 1987, when MAbs were regularly produced in rodents for diagnostics.


Monoclonal antibodies

Monoclonal antibodies

Antibodies produced from a single clone of B cells.

Produced by fusing a B cell secreting the desired antibody with a myeloma cell capable of growing indefinitely in tissue culture.

Monoclonal antibodies all have identical antigen-binding sites. Thus they all bind to the same epitope with the same affinity. They are all of the same antibody class (isotype).


Hybridomas technique

Hybridomas Technique

B lymphocytes can mutate into tumor cells that result in a type of cancer termed myeloma.

- Myeloma cells become “immortal” and will grow indefinitely in culture.

- Fusion of a single activated B cell and a myeloma cell will create a hybridoma that can grow indefinitely in culture


Hybridoma selection the hat trick

Hybridoma SelectionThe “HAT Trick”

Myeloma cells have been genetically engineered such that they can not use hypoxanthine, aminopterin, and thymidine (HAT medium) as a source for nucleic acid biosynthesis and will die in culture.

Only B cells that have fused with the engineered myeloma cells will survive in culture when grown in HAT medium.


Immunoglobulin and monoclonal antibodies

spleen

Monoclonal Antibodies

Purified antigen

molecule

Inject antigen into mouse

Kill the mouse and remove

the spleen (containing antibody

generating cells)


Immunoglobulin and monoclonal antibodies

spleen

fuse

“immortalized”

cell

+

Each cell may have produced a different antibody

dissociate

A Hybrid cell that can be cultured


Immunoglobulin and monoclonal antibodies

Select one of these "hybrid" cells to subculture….

… and produce a

mono clonal population


Immunoglobulin and monoclonal antibodies

USES

Measuring protein and drug levels in serum

Typing tissue and blood

Identifying infectious agents

Identifying clusters of differentiation for the classification and follow-up therapy of leukemias and lymphomas


Immunoglobulin and monoclonal antibodies

USES

Identifying tumor metastasis

Identifying and quantifying hormones

Immuno affinity Purification

Used in several diagnostic tests to detect small amounts of drugs, toxins or hormones, e.g. monoclonal antibodies to HCG used in pregnancy test kits or diagnosis of AIDS by the ELISA test.


Immunoglobulin and monoclonal antibodies

USES

monoclonal antibody can be coupled to another molecule like a fluorescent molecule to aid in imaging the target

Or with a strongly-radioactive atom, such as Iodine-131 to aid in killing the target.

Used in the radioimmuno detection and radioimmuno therapy of cancer, and some new methods can even target only cancerous cells.


Immunoglobulin and monoclonal antibodies

USES

Monoclonal antibodies can be used to treat viral diseases, traditionally considered "untreatable". In fact, there is some evidence to suggest that antibodies may lead to a cure for AIDS.

Monoclonal antibodies can be used to classify strains of a single pathogen, e.g. Neisseria gonorrhoeae can be typed using mAB.

To identify and to trace specific cells or molecules in an organism.


Immunoglobulin and monoclonal antibodies

USES

OKT3 (immunosuppressant) an antibody to the T3 antigen of T cells, is used to alleviate the problem of organ rejection in patients who have had organ transplants.


Immunoglobulin and monoclonal antibodies

Affinity chromatography:

Bind antibody to a support matrix (e.g. sepharose gel)

Add protein mixture - antigen binds to antibody on support

Wash to remove unbound material

Lower pH - antibody releases the antigen - which is now free of contaminants


Immunoglobulin and monoclonal antibodies

Affinity chromatography - antibody purification.

Antigen can be bound to the support matrix in order to purify antigen-specific antibody from a polyclonal antiserum.

From http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AffinityChrom.html


Immunoglobulin and monoclonal antibodies

Tumor diagnosis

in vitro

in vivo

99mTc-mAb


Monoclonal antibodies for cancer treatment

Monoclonal antibodies for cancer treatment

Three mechanisms that could be responsible for the cancer treatment.

1. mAbsact directly when binding to a cancer specific antigens and induce immunological response to cancer cells. Such as inducing cancer cell apoptosis, inhibiting growth, or interfering with a key function


Monoclonal antibodies for cancer treatment1

Monoclonal antibodies for cancer treatment

2. mAbscan be modified for delivery of a toxin, radioisotope, cytokine or other active conjugates.

3. it is also possible to design bispecific antibodies that can bind with their Fab regions both to target antigen and to a conjugate or effector cell


Drawbacks of monoclonal antibodies

Drawbacks of Monoclonal Antibodies

Since monoclonal antibodies produce antibodies to a single determinant, they do not form the lattice necessary for precipitation and so cannot be used in precipitation assays,

radial immunodiffusion, immunoelectrophoresisor agar gel diffusion.

Very high titer antibodies also pose certain difficulties


Immunoglobulin and monoclonal antibodies

Any question ……

Thank you all


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