Immunology Interview Questions and Answers
What are
iccosomes?
The particles coated with immune complexes and are released
from follicular dendritic cell extensions, are called as iccosomes.
What is an incomplete
antibody?
Antibody can bind to an antigen but cannot induce
agglutination is called incomplete antibody.
What is opsonin?
Opsonin is a substance, which promotes phagocytosis of
antigens by binding to them.
What is a myeloma
protein?
It is a monoclonal immunoglobulin produced from a myeloma
cell.
What is delayed
hypersensitivity?
We can recognize the Symptoms only days after exposure. This
is delayed hypersensitivity (DTH).
What is
hypersensitivity?
The inflammatory response produced by inflammatory molecules
result in tissue damage and some times even death. We call this as
hypersensitivity or allergy.
What is
anaphylaxis?
It is most rapid hypersensitive reaction. It responds within
minutes of applying a stimulus and can get localize. Reactions are mediated by
release of pharmacologically active substances.
Give the classification of
hypersensitivity.
Hypersensitivity is classified into five types-
- Anaphylaxis
- Antibody dependant
cytotoxicity
- Immune complex mediated
diseases
- Delayed type ‘o’ cell
mediated hypersensitivity
- Stimulatory
hypersensitivity
Name the scientists who classified
hypersensitivity.
Coombs and Gell
What are hypersensitive
reactions?
If humoral or cellular immunity is switch on to high for
length of time, tissue damage may occur. Such reactions are called
hypersensitive reactions.
What is auto
immunity?
Disease caused by immunological reaction to self-antigen.
Such type of diseases is classified either organ specific or non-organ specific.
Name some of the immuno
suppressive agents.
- Cytotoxic agents such as
chlorambucil, cyclophosphamide, and azathioprine
- Glucocorticoids
- Cyclosporine
- Antilymphocyte
antibodies
What is immuno
suppression?
Immuno suppression is particularly given to the patients who
are undergoing organ transplantation in the treatment of autoimmunity, graft
rejection and in allergy conditions.
What are the types in
adjuvants?
- Organic adjuvants
- Synthetic adjuvants
- Tuftsin
What is an
adjuvant?
Adjuvant potentates the immune response Vaccines need to be
enhanced by some substances, these substances are called adjuvants.
What is
vaccination?
Vaccination means exploiting the immune system to protect
against infectious diseases. Vaccination is done to protect against lethal
diseases such as mumps, rubella, poliomyelitis, diphtheria, tetanus, small pox
etc.
What is
attenuation?
Natural behavior of an organism without causing disease is
called attenuation i.e. reducing pathogenesity of the organism.
What is secondary immune
response?
Secondary immune response occurs when second exposure to the
same antigen occurs after weeks, months or after years.
What is inductive or latent
period?
After immunogen is introduced no antibody is detected, this
is latent or inductive period. In this period, immunogen is recognized as a
foreign substance.
What is primary immune
response?
First exposure to an antigen produces primary immune
response.
What is a binder?
The binding protein (usually antibody) which binds to the
ligand is called as binder.
What is an analyte or
ligand?
The substance whose concentration is to be determined is
called as an analyte or ligand.
What is importance of radio immuno
assay?
It is the most sensitive technique used for detecting antigen
or antibody. This type of reaction is also called as binder ligand assay.
In radio immuno assay what is the
used to label an antigen?
In this technique, the antigen is generally labeled with a-
emitting isotopes such as I125.
What is radio immuno
assay?
It is a competitive binding assay in which fixed amount of
antibody and radiolabelled antigen react in the presence of unlabelled antigen.
What is western
blotting?
Identification of specific protein in a complex mixture of
proteins can be accomplished bye a technique that is known as western blotting.
What are the enzymes used for
labeling of antibodies?
Enzymes used for labeling of antibodies are horseradish
peroxidase, alkaline phosphatase, ß- galactosidase, lacto preoxidase, etc.
What is the significance of
indirect ELISA?
It is used for the detection of the presence of serum
antibodies against immuno deficiency virus (HIV, the causative agent of AIDS).
In how many ways ELISA can be
carried out.
It can be carried out in three ways.
Indirect ELISA
Sand witch ELISA
Competitive ELISA
What is the significance of
ELISA?
It is used for the detection and for identification of either
antigen or antibody.
Name two enzymes that have been
employed for ELISA.
- Alkaline, phosphatase,
horseradish, preoxidase
- Para nitro phenyl
phosphatase
What is the basic principle of
ELISA?
The basic principle is an enzyme conjugated to n antibody
reacts with a colorless substrate to generate a colored product.
What is the full form of
ELISA?
Enzyme Linked Immuno Sorbant Assay.
What are the uses of indirect
immuno fluorescence?
- For identifying bacterial
species
- Detecting antigen-antibody
complexes in autoimmune diseases
- Detecting compliment
components in tissues.
- Localizing
hormones
What are the advantages of
indirect immuno fluorescence?
The primary does not need to be conjugated with label.
It increases the sensitivity of staining because multiple fluorochrome reagents will bind to each antibody molecule.
This method has great flexibility.
What is indirect immuno
fluorescence?
In a method the primary unlabelled antibody is detected with
a number of reagents have been developed for indirect staining. The most common
is fluorescence labeled anti isotype antibody such as fluoroscin labeled goat-
mouse antibody.
What is the disadvantage of direct
immuno fluorescence?
A separate fluorescent conjugate have to be prepared against
each antigen to be tested.
What is direct immuno
fluorescence?
In this method, the species antibodies are primary
antibodies, which are directly conjugated to fluorescent dye.
Into how many types is immuno
fluorescence is divided?
Immuno fluorescence is divided into 2 types-
- Direct immuno fluorescence
- Indirect immuno
fluorescence
What are the most commonly used
fluorescent dyes?
The most commonly used fluorescent dyes are fluorescin or
rhodamine. Both dyes can be conjugated to Fc region of antibody without
affecting the specificity of the antigen.
What is immuno
fluorescence?
Fluorescence is the property of absorbing light ray of
particular wavelength and emitting rays in different wavelength.
Antigens that are bound to cells or tissue sections can be
visualized by tugging the antibody molecule with a fluorescent dye or
fluorochrome.
Give application of counter
current immuno electrophoresis
This technique is applied to detect the antibody against
hepatitis-B and to detect antibodies against SLE (systemic leupus
erythromotosis) and used to detect specific antigen foe- meningo coccus in
cerebrospinal fluid.
What is counter current immuno
electrophoresis?
This technique involves the simultaneous electrophoresis of
antigen and antibody in the gel in the opposite direction resulting in
precipitation of point where there is optimum concentration of antigen-antibody.
This method produces visible precipitin with in 30 minutes
and is 10 times more sensitive than the standard double diffusion technique.
Give some applications of immuno
electrophoresis.
- This technique is useful for
testing normal and abnormal proteins in serum and urine.
- It is useful to determine
whether a patient produces abnormally a low amount of one or more proteins.
- It is also used if a patient
over produces some serum proteins.
How is immuno electrophoresis more
advance than paper electrophoresis?
In paper electrophoresis, serum proteins can be separated
into 5 different bands but the same protein using immuno electrophoresis can be
separated into 30 different proteins.
What is immuno
electrophoresis?
The resolving power of immuno diffusion was greatly enhanced
bye immuno electrophoresis. This involves the electrophoretic separation of
antigen into its constituent proteins followed by immuno diffusion.
This technique is performed on 1% agarose gel. Antigen
mixture is first electrophori zed and separated based on charge, troughs are
then cut in the agarose gel, and antiserum is added to the troughs.
The agarose gel is then incubated 18-24hrs during which the
antigen and antibody diffuse towards each other. The formation of precipitin
bands can be observed for the individual antigen components.
What is double immuno diffusion
method?
In this method, both antigens and antibodies diffuse
radically from wells towards each other by establishing a concentration
gradient. As equivalence is reached, a visible line of precipitation is
observed.
The patterns of precipitin lines that are formed when two
different antigens are placed in adjacent wells indicate whether they share any
common epitope or not.
Identity occurs when two antigens share identical epitopes;
hence, the line of precipitation formed by them will fuse to give single curve
line of identity.
Non-identity occurs when two antigens are unrelated. The
antiserum form independent precipitin lines that cross each other.
Partial identity occurs when two antigens share common
epitope. The antiserum forms line of identity with the common epitope and a
curved spur with the unique epitope.
What is the limitation for radial
immuno diffusion method?
This method cannot the antigens present in concentration
below 5-10 micro grams/ml.
What is radial immuno diffusion
method?
It is used to qualitate the antigen. Suitable dilution of
antiserum is incorporated in the agar gel. Antigen is added to the wells cut on
the surface of the gel. As the antigen diffuses into the agar region,
equivalence is established and ring of precipitation is formed. The area of
precipitin ring is directly proportional to the concentration of antigen. By
comparing the area of precipitin with a standard curve obtained by measuring the
precipitin area of known concentration of antigen, the concentration of antigen
in the given sample can be determined.
Name the two-immuno diffusion
techniques.
- Radial immuno diffusion
method and
- Double immuno diffusion in
two dimensions
What are immuno diffusion
reactions?
These reactions can be used to determine relative
concentrations of antigens and antibodies to compare antigens and to determine
the relative purity of an antigen. They are mainly preformed in 1% agarose gels.
What are the applications of
precipitation reactions?
- Precipitation reaction is
the basic reaction for a number of techniques.
- It is less sensitive for
detecting antibodies.
- Precipitation reactions in
gels have several advantages rather than in liquid medium.
- They have forensic
application in identification of blood and seminal stains.
What is zone of
equivalence?
In this, ratio of antigen-antibody is seen optimal which
results in large multimolecular lattice, hence maximum precipitation is
observed.
What is zone of antibody
excess?
In this, the first available antigen is completely filled by
antibody molecules. Hence, no antigenic determinant is left out free. Unreacted
antibody is seen in large amount, hence poor lattice formation.
What are the three distinct phases
that a precipitation shows?
The three distinct phases are
Ascending part called ‘zone of antibody excess’.
A peak called ‘zone of equivalence’.
A descending part called ‘zone of antigen excess’.
Give the mechanism of
precipitation.
Marrak proposed the lattice hypothesis to explain the mechanism of precipitation.
The amount of precipitate formed is greatly influenced by relative proportions of antigens and antibodies.
The valency of antigens is multivalent.
When antigen-antibody is in optimal concentration, the
precipitation is complete. So that, large lattice is formed.
Briefly describe about
precipitation reaction.
When a soluble antigen combines with corresponding antibody
in the presence of electrolyte at a suitable temperature and pH, the
antigen-antibody complex forms an insoluble precipitate .Antibodies that form
precipitate ate called precipitants.
Into how many types is
antigen-antibody reactions are broadly classified?
It is broadly classified into five-
- Precipitation
- Agglutination
- Complement fixation
- Immunoassay using labeled
reagents
- Immunohistrochemistry
(Immunoflourescence)
What is horseman
antigen?
The glycolipid antigens are present in most tissues of guinea
pigs but not in the RBC. They are found in gastrointestinal mucosa in some
people. This horseman antigen will not induce antibody formation.
What are heterophile
antigens?
Heterophile antigens are polysaccharides, which are
structurally similar because of their limited complexity. They are derived from
members of widely separated taxonomic groups.
Give an example of
cross-reaction.
Cross reactivity is often observed in polysaccharide antigens
that contain similar oligosaccharide residue. A, B, O blood group antigens -
These are glycoprotein expressed on RBC.
What is a
cross-reaction?
Antigen-antibody reactions are specific, but in some cases
antibody elicited by one antigen can cross react with another antigen. This
reaction is called as cross-reaction and the antigen that produces
cross-reaction is called as cross-reactive antigen. Cross-reaction is due to the
presence of two or more antigenic determinants on the related antigen.
What is avidity?
The capacity of an antiserum containing various antibodies to
combine with the whole antigen is called avidity. Thus, avidity is used to
denote the overall capacity of an antibody to combine with multivalent antigen.
A multivalent antigen has many types of antigenic
determinants, when this is injected into the blood each antigenic determinant
stimulate the production of particular antibody.
What is affinity of an
antibody?
The strength of binding of an antibody to a monovalent
antigen or single antigenic determinant is called affinity of an antibody.