The use of quantitative immunocytochemistry (QICC) to measure calbindin D28k-like immunoreactivity in the rat brain.

We have developed a method of quantitative immunocytochemistry using an iodinated second antibody to visualise the anatomical distribution of primary antibodies in tissue sections, by macroautoradiography. Computer-assisted densitometry was used to analyse the pattern of optical densities within autoradiograms. The amount of antigen present in tissue sections was then quantified by comparison with non-biological standards which were processed in parallel with the tissue sections. Using this technique we have measured calbindin like-immunoreactivity in 4 areas of rat brain and have found that the values obtained are similar to those obtained by radioimmunoassay. A similar approach can be used to quantify autoradiograms by comparison with antigen standards to measure amounts of radiolabelled immunoreactivity and determine concentrations of biologically active molecules in discrete brain areas.