An in vitro assay for uni-directional migration inhibition employing 51Cr-labelled macrophages.

An improved in vitro technique to assay for migration inhibitory factor is presented. The method employs chromium-51-radiolabelled guinea-pig macrophages and offers significant advantages including (1) elimination of observer to observer variation and tedious measurements resulting in an objective and technically simple assay, (2) the requirement for small numbers of immune lymphocytes, (3) good sensitivity and reproducibility between successive assays performed on different days, and (4) a means of obtaining relative estimates of the 'strength' (concentration) of the factor so that comparisons with healthy individuals can be made.