Serological reactions like precipitation, agglutination, complement fixation and neutralization tests are used to detect antibodies and antigens. Precipitation reactions form visible precipitates when antigen and antibody interact and form lattices. Immunodiffusion techniques like Ouchterlony and immunoelectrophoresis allow antigen-antibody reactions to be visualized as precipitin lines or arcs in agar gels. Agglutination reactions cause visible clumping when particulate antigens react with specific antibodies.

2. •Precipitation reaction.
•Agglutination reaction.
•Complement fixation test.
•Neutralization test.
•Opsonization.

3. •Easiest serological rxn.
•Ag & Ab interact & form lattice which develops
into visible precipitate.
•Ppt . is best observed when ag & ab are in optimal
proportions(equivalence point).
•Polyclonal ab form lattice /large aggregates than
monoclonal.
•All ag & ab bindings are reversible.

4. •It’s a curve that displays the amount of ag /ab
complexes precipitated while keeping the ab conc.
constant & increasing ag conc.
•Equivalence zone : free reactants are in
equilibrium with bound
reactants(ag & ab).
-Maximum precipitation .
-large insoluble complexes of
ag & ab.

5. Zone OF Ab Excess : precipitation is inhibited
ab bound to ag is detected
easily as ab is excess &
ag is less.
Zone Of Ag Excess : precipitation inhibited .
Ab gets filled as Ag conc.
increases.
unbound Ag found at the
supernatant .

7. •Ring test
•Slide test
•Tube test
•Immunodiffusion
SD in 1D
SD in 2D
DD in 1D
DD in 2D
Immuno electrophoresis
•Electro immunodiffusion
Counter immunoelectroporesis
Rocket electrophoresis

8. •Done in test tube.
•Soluble Ag is layered over ab.
•Precipitation occurs at interface of 2 reagents.
•Agar solution is layered over column of Ab in
tube.
•Simple , qualitative & can be done in agarose.
•Eg- Ascolis thermo precipitin test.

10. •Done in slide.
•Drop of At & Ab are
placed on slide
•Mixed by shaking
•Floccules appear.
•VDRL test for syphilis

12. •Serial dilutions of toxins/toxoid added to
tubes.
•Fixed antitoxins.
•As its diluted using tubes its named tube test.
•Max precipitation occurs in the tube where
At & Ab are in equal proportion.
•Eg- Khan’s test for Syphilis

14. •Ouidin procedure.
•Preformed in soft agar(1%).
•Result is Visible & retained .
•Ab incorporated into agar at low temp
(molten sate).
•Ag is layered over it.
•Ag diffused downward.
•Band is observed in agar containing Ab .

15. •Oakley procedure.
•Ab incorporated into gel at the
bottom of tube.
•Followed by plain agar film.
•Ag is layered above it.
•Band is formed in plain agar as both
diffuse.
•Ag downward & Ab upward.

17. •Radial immuno diffusion/Mancini reaction.
•Done in special square slide / petridish.
•Agar incorporated with Ab is poured into the
slide(3mm).
•Solidified.
•Wells are cut & Ag is loaded into the wells.
•Precipitin rings form as Ag diffuses out in all
directions.
•Radius of rings are measured & calculated
using standard ring diameter.

19. •Ouchterlony reaction.
•Plain agar of 3mm poured over slide /
petridish.
•Antibody is loaded onto central well.
•Antigens to surrounding wells.
•At & ab diffuse from their wells into plain
agar medium.
•Based on simultaneous application of at &
ab.

20. A-patients sample
B-standard sample
a- antibody
Smooth lines of identity b/n Ag of patient & std.
Ag signifies they are the same.
Same reactions with Ab.
Solid continuous line
If multiple wells of Antigens are positioned
around antibody on the same plate several
patterns can be observed
A
a
B

21. A- antigen 1
B-antigen 2
a-antibody
When both antigens are different they react
differently with Ab.
Cross precipitin bands are formed.
Double spur i.e line of non identity
A
a
B

22. A-patients antigen
B-control
a-antibody
When A & B share a common element but
are not exactly the same.
Single spur is formed.
Line of partial identity.
A
a
B

23. •Electrophoretic separation of composite
antigen( serum of patient) into its constituent
parts/proteins.
•This is followed by immunodiffusion against its
antiserum.
•Test serum loaded into well
•Antibody is loaded into troughs cut in gel.
•18-24h diffusion occurs.

25. Development of precipitin lines is
enhanced by electrically driving Ag &
Ab movement.

26. •Reaction b/n migrating Ag & Ab
during electrophoresis.
•Move towards each other resulting in
precipitation at a point.
•Used only when Ag & Ab have
opposite charges.
•Its fast.

28. •Done for quantitative estimation of Ag.
•Antiserum is incorporated into gel.
•Ag in increasing conc (single Ag) loaded in
wells.
•Precipitation reaction results in rocket
shaped precipitin formation.
•Distance from the well to the front of
rocket shaped arc is related to Ag conc.

30. •Reaction b/n Ab(agglutinins) & particulate
Ag(agglutinogens).
•Causes visible clumping.
•More sensitive than precipitation reaction.
•Incomplete / monovalent Ab do not cause
clumping.

31. •On a slide a drop of
Ag is taken.
•Drop of saline added.
•Drop of antisera.
•Clearing of drop by
clumping.
•Visible under naked
eye.

33. •Quantitative method for estimation of Ab.
•Fixed volume of Ab is added to equal vol of
serial dilutions of an antisera .
•Eg-typhoid (widal test).
•Antigens H & O (flagellar & fluffy clumps)

35. • Detect anti- Rh antibody that do not agglutinate Rh +
erythrocytes in saline.
•Anti Rh is mixed with Rh +ve RBC .
•This sensitizes Ab on surface of RBC .
•Unbound Ab is washed free.
•Anti human Ig is added.
•Agglutination occurs.

37. Highly sensitive for small quantities of Ag.

39. •Based on ability of Ag-Ab complexs to fix complexes.
•Ag & Ab are mixed well.
•known complement is added to the complex.
•Incubated at 4degree for 18h.
•Hemolysin sensitized RBC serves as indicator(to destroy
rbc).
•But no lysis occur as complement is engaged/bound to
complex.(patients)
•But in healthy individual lysis occurs as Ab is absent.

41. •Viral neutralization test : neutralization of virus by
antibdy.
•Eg-plague inhibition test for bacteriophage.
•Toxin neutralization : bacterial endotoxin are good
antigens they induce Ab formation.
•Eg – diphtheria & tetanus
•An Ab that bind to foreign molecules makes it more
susceptible to phagocytosis.

42. •Opsonin enhances phagocytosis.
•Mark antigens for immune response / mark dead cells
for recycling.
•Opsonization :
•Mechanism by which microbes are chemically
modified to have to have a stronger attraction to the
surface receptors on phagocytes & NK cells.
•Binding makes it easy for destruction of the antigen.