Haemagglutination Experiment :

• In wells where enough influenza virus is present, all the RBCs have agglutinated (i.e. are linked together in a 3-dimensional matrix), like this:

• In wells where the concentration of influenza virus has been diluted below a critical point (1 HAU), the cells settle out at the bottom of the well to form a "button" like this:

On the plate above, click on the endpoint of the assay - i.e. the last well in which all the RBCs have agglutinated.