FUNCTIONAL AND AUTOLOGOUS IMMUNE RESPONSES OF CRYOPRESERVED HUMAN LYMPHOCYTES
Various studies have indicated that frozen cell storage provides a means of repeating and extending immunological assays involving the same lymphocyte cell sample. We and others have demonstrated that lymphocytes retain their ability to respond to antigens of dental interest as well as to polyclonal B-cell activators (PBA) and superantigens (SA) after short term frozen storage. The objectives of this study were to determine whether lymphocytes retain functional and cytokine activity after 6 months in frozen storage and whether autologous immune responses are retained by unstimulated frozen lymphocytes. Peripheral blood mononuclear cells (PBMC) from four normal human subjects were frozen using a Cryomed Model 1010 programmable freezing system and stored in liquid nitrogen. At intervals thereafter, portions of each sample were assayed for blastogenic responses and cytokine production (IL 1,2, and TNF) after stimulation by a variety of lymphocyte stimulators including PBA and SA. Our results indicate that frozen and stored lymphocytes retain a variety of functional activities after 24 weeks in liquid nitrogen storage. The most constant responses were observed among autologous immune responses. Frozen storage continues to represent a viable method of extending immunological analysis of clinically characterized subjects.