Natural cell-mediated cytotoxicity: a micro assay suitable for clinical tests.

A micro version (microtest, MIT) of the 51Cr release assay for detecting Natural Killer activity (NK) has been developed. The test retains the sensitivity and the efficiency of conventional macroassay (macrotest, MAT) and provides a 5-fold reduction in the number of effector and target cells employed. In experiments performed with peripheral blood mononuclear cells (MNC), untreated or treated with interferon (IFN) or with hydrocortisone (Hy), comparable values of the percentage of specific lysis and of the number of lytic units were obtained using both MAT and MIT methods. Therefore MIT appears to be useful in monitoring the NK function of patients characterized by low MNC counts.