Direct bovine leukocyte migration inhibition assay: standardization and comparison with skin testing

A direct leukocyte migration inhibition (LMI) assay under agarose was standardized for use in cattle. The procedure included maintenance of culture conditions at pH 7.4 in a humidified, 39 C incubator with 98% air and 2% CO2. Optimum demonstration of incubation was obtained using a 9-hour incubation period. The LMI assay was used to detect reactivity to keyhold limpet hemocyanin (KLH) and horseshoe crab hemocyanin (HCH). Calves sensitized to KLH had specific reactivity for KLH and occasional reactivity for HCH. Similarly, calves sensitized to HCH showed reactivity for HCH and occasional reactivity for KLH. The nonspecific reactivity in the LMI was more frequent after skin testing with both antigens. Specific association of LMI reactivity and DTH reactivity was found in 8 of 10 animals. There were no nonspecific skin test responses. The results suggest that consecutive LMI assays are required to establish trends in reactivity and these should be used in conjunction with other in vitro assays of cellular immune reactivity.