Abstract
We have investigated the in vitro transformation of lymphocytes that have been frozen and stored at low temperatures. Cells frozen at different times and stored for various times do transform in a reproducible manner when placed in culture with PHA or as one population of the two-way or the one-way MLR. When frozen-stored lymphocytes are cultured with specific antigen or as both partners in the MLR the response is minimal. The freezing process destroys neutrophils, and the remaining population transforms in a manner similar to cultures of purified lymphocytes. Practical aspects of the technique are discussed and we have suggested possible practical applications for future investigation.