TCD

[Jay and Nancy Mone]

The tissue culture infectious dose (TCID50) is a quantal assay for 
infectivity.  It involves inoculating replicate wells or flasks of 
susceptible cells with dilutions of a virus suspension, and determining 
what dilution will yield infection of 50% of the replicate cultures.  The 
actual calculations go by the names Spearman-Karber(?) or Reed-Meunsch 
methods, but give you the same info.  These assays don't tell you how 
many infectious particles are in the suspension, but only the infectivity 
of the suspension in tissue culture.  I can send you examples if you're 
interested.

Jay Mone'