A new assay for rapid measurement of MIF levels by 3H-labelled cells in liquid scintillation counting vials: Statistical implications for the measurement of migration inhibition

Abstract

A new quantitative assay for migration inhibitory factor (MIF) employs 3H-labelled cultured mouse or human lymphoid cells migrating from capillary tubes. Capillaries filled with labelled cells are placed in liquid scintillation counting vials, along with the MIF- containing sample and are removed at the end of a five-hour incubation period. The residual, labelled cells which have migrated out of the tubes are solubilized and counted in a liquid scintillation counter. While cultured lymphoblast cells are routinely used in the assay, the method was checked against mouse and guinea pig peritoneal exudate cells in both the labelled cell technique and the conventional chamber assay. The assay is technically simple to perform and a useful tool for laboratory research purposes because of the short span of time needed to obtain the results. These advantages indicate a potential for automation and use of this assay in a clinical immunology laboratory. Statistical analysis of data from both assays demonstrated that the relative variation among replicates is lower in the labelled cell assay. The new assay also measured a significant difference between controls and MIF-containing samples when the migration index (MI) was greater than 80%. Criteria for significant inhibition of migration are discussed in regard to the use of analysis variance (ANOVA) and other statistical procedures, and the inadequacy of a single measure, such as the MI, is discussed.