The use of cryopreserved lymphocytes for longitudinal studies of immune function and enumeration of subpopulations.

The responses of fresh and frozen lymphocytes to mitogens and antigens have been compared using samples collected on five separate occasions from one normal donor. The day-to-day variation seen with the fresh cells was eliminated by the use of frozen cells. Thawed cells from one donor collected on one occasion but studied on five separate occasions and compared to fresh cells on the same days, showed fluctuations from day to day as well, confirming that the day-to-day variation seen is due to technical and not biological phenomena. Cryopreserved cells showed a decrease in responses to specific microbial antigens, a slight shift in the PHA dose-response curve, but no significant difference in responses to Con A or PWM. The relative proportion of lymphocyte subpopulations changed with freezing and thawing. The proportion of T cells increased slightly and the proportion of B cells decreased.