Exercise 1: Serial Dilutions and Liquid Precipitation

solvent

medium making up the rest of the solution in a dilution

solute

the material being diluted in a dilution

how do you calculate the new concentration after a dilution?

multiply the initial concentration by the dilution factor

serial dilution

successive dilutions of a sample

titer

reciprocal of antibody dilution in the last tube in which a reaction is visible (express in whole number)

acute samples

taken at the on set of symptoms

convalescent samples

taken 5-7 days after the onset of symptoms

what shows a recent or ongoing infection?

a fourfold increase of the convalescent sample after being run at the same time as the acute

precipitation

When an insoluble complex is created from combining a soluble antigen and an antibody

anitbody

protein produced by a differentiated B cell or a plasma cell

zone of equivalence

when antibodies and antigens are in optimal proportions; when a lattice formation forms

what factors influence precipitation reactions?

the zone of equivalence and whether an antigen is bivalent or monovalent

liquid precipitation

the simplest method

mixed in a tube 

Cloudiness is measured 

precipitin rings form in ZOE

Fluid phase precipitation 

in a capillary tube 

qualitative test

solutions diffuse towards each other and create a band of precipitation when in ZOE

Gel precipitation

pores in a semi-solid medium allow molecules to move, where size determines the rate of diffusion 

can be single or double diffusion 

single diffusion 

Either antigen or antibody is diffused through the gel while the other is in a well 

example: RID

double diffusion

both antigen and antibody diffuse through the gel

the known substance is in a central well surrounded by other wells of the unknown substance 

lines of precipitation form in ZOE

prozone

anitbody in excess

post-zone

antigen in excess

why is it important that each antigen have at least two determinants per molecule?

being connected to two different antibodies allows the lattice to form 

Why would a patient with a known high antibody titer return a false negative?

there is too much antibody meaning it is a prozone phenomena

if the patient with a known high antibody titer returns a false negative, how would you fix this?

dilute the sample and rerun the test