Cryopreserved human cultured T cells as responder cells for the quantitative measurement of interleukin-2: improvement of the assay.

Large batches of human cultured T cells (CTC) were cryopreserved for later use as responder cells in a proliferation assay for measurement of interleukin (IL)-2 activity. Cryopreservation of CTC could be carried out without considerable loss in viability and cryopreserved and fresh cells showed equally good responses to IL-2. The conditions of IL-2-dependent CTC growth were analyzed, which led to a better evaluation of test results, and had important implications for the calculation of relative IL-2 activity. The repeated use of the same batch of cryopreserved CTC reduced test variability and provided an assay system that allows reliable and reproducible measurement of human IL-2 activity.

Effect of sonic treatment on pure cultures and aggregates of bacteria.

Pure cultures of a variety of bacteria were treated with ultrasonic energy using a sonic probe. Fractions of organisms killed at different sonic energies were calculated, and Streptococcus mutans was 600 times more resistant than Fusobacterium nucleatum, the most sensitive organism tested. The effects of sonic treatment on aggregates of bacteria were examined, and the results were interpreted as a model of the events that probably occur during the sonic dispersion of dental plaque.