Cytokine production by cryopreserved human peripheral blood mononuclear cells in response to periodontal pathogens

Freezing techniques provide a way of repeating and extending immunological assays by using frozen portions of an individual's peripheral blood mononuclear cell fraction. Earlier work shows that the lymphocytes that are stored frozen retain their ability to respond to polyclonal B-cell activators, mitogens, superantigens and bacterial extracts of oral interest. These studies extend previous findings by determining cytokine production by lymphocytes following frozen storage for up to 24 weeks. Production of interleukin (IL)-1beta, IL-2, IL-6, and tumour necrosis factor (TNF)-beta by stimulated lymphocytes after cyropreservation was not significantly different from those responses before storage, with one exception: IL-6 production was negligible after 24 weeks' frozen storage when thawed cells were cocultured with pokeweed mitogen. After stimulation with extracts from Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans, the proliferative capacity of the frozen cells was maintained as well as the production of IL-1beta, IL-2, and IL-6. TNF-beta was not produced in response to bacterial antigen stimulation. The ability of peripheral blood mononuclear cells to retain functional activity after frozen storage should permit more effective monitoring during longitudinal clinical studies and a better evaluation of changes in cytokine production in patients with advanced periodontitis both during and after treatment.