That depends on the tissue. the aim is to get a one-cell-layer section for mostly any preparation. So the diameter of the predominant cells is your guideline. Think about lymphoid cell versus adipose cells ....

For FISH on FFPE lymphoid tissue we cut at 1 µm (setting on the microtome). the thinner the section the less autofluorescence disturbs. As the setting on the microtome never gives the "real" thickness of the slide and as there are differences from microtome to microtome, it should be tested in a small serie.

Hi as Gudrun said above it rather depends on your tissue and intentions but very generally most people will section at 5-10 microns. The thicker the sections the easier they are to handle etc. but often the images get less "sharp" the thicker the sections are.

I found 10 microns sections suitable for MTC and  IHC on lung tissue. Personally I would start trying to section quite thin and take increasingly thicker sections until you are happy that you can cut and capture successfully (i.e. 3 micron, 5 micron and 10 micron).

If in doubt check the literature for your tissue and (if available) the antibody you wish to use and see what people are using. For some tissues (especially over-fixed) you may have to use aggressive AR to open an epitope. If this is the case (or you think it might be) you may wish to pre-coat the glass slides with a substance to help the sections stick/ survive. I found APE treatment quite good for this (below).

Subbing slides with APES.

1.    Make up 2% APES by adding 5 ml of APES (Sigma, 741442) to 245 ml of Acetone (Sigma, 534064) in a histology dish in the fume hood. Place the rest of the Acetone (250 ml) in a separate dish.

2.    Place 25 slides (in a rack) in the 2% APE for 30  min at room temperature. After this remove slides and rinse in second dish of Acetone 2 x and air-dry. After this time place the slides in a slide box and store at 4oC until required.

Hope this helps,

Gary

Hi, if you mean the thickness I will agree with Gudrun Lang and Gary Morley. But if you intend the diameter, I already cut  nervous tissues up to 4 cm diameter. It was better in case of thicker sections (6 micron better than 4 micron) to get the complete section and image for the whole structure (at low maginfication).