Cellular and molecular mechanisms of the IL-12-induced increase in allospecific murine cytolytic T cell activity. Implications for the age-related decline in CTL.
The mechanism(s) by which IL-12 augments CTL generation and the potential for IL-12 to alter the age-related decline in CTL activity were assessed using primary CTL stimulated by allogeneic cells. IL-12 at 2 U/ml enhanced the generation of allospecific CTL response in young adult mice by 1.5- to 5-fold, and optimal augmentation was achieved and maintained with as low as 0.1 U/ml IL-12. In contrast to the enhancement of MHC-unrestricted lytic activity, which was most efficient when IL-12 was added near the end of the 5 day culture period, nearly equivalent augmentation of Ag-specific CTL was induced when IL-12 was added from 1 to 5 days before harvest. The augmentation of CTL by IL-12 was not associated with increased incorporation of [3H]TdR. Increased IFN-gamma production was not required for IL-12 to augment CTL activity because when three different Abs against mouse IFN-gamma were each included in the MLC at concentrations abolishing recoverable IFN-gamma protein, they did not inhibit the IL-12 effect but, under some conditions, further increased CTL activity. Ab to IL-2 also did not alter the IL-12 effect. Depletion of ASGM1+ cells from the responding population before stimulation did not significantly alter the response to IL-12. However, depletion of CD8+ T cells from effector cells obtained after stimulation substantially reduced the IL-12-induced augmentation of CTL. Thus, the results suggested that IL-12 augments CTL activity primarily through an effect on T cells, and the augmentation was associated with an approximate doubling of perforin levels, which was not caused by a significantly increased proportion of CD8+ cells. Finally, IL-12 was effective for moderating the age-related decrease in CTL activity, suggesting a potential role for immunomodulation by IL-12.
Bloom
E T
ET
Laboratory of Cellular Immunology, Food and Drug Administration, Bethesda, MD 20892.
Horvath
J A
JA
D000375:Aging / Q000276:immunology*; D000818:Animals; D016827:CD8 Antigens; D003602:Cytotoxicity, Immunologic; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D005677:G(M1) Ganglioside / Q000378:metabolism; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12; D007376:Interleukin-2 / Q000276:immunology; D007378:Interleukins / Q000008:administration & dosage / Q000494:pharmacology*; D007519:Isoantigens; D015979:Killer Cells, Lymphokine-Activated / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology; D008213:Lymphocyte Activation; D008285:Major Histocompatibility Complex; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism
D016827:CD8 Antigens; D007376:Interleukin-2; D007378:Interleukins; D007519:Isoantigens; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D054353:Perforin; D018664:Interleukin-12; D005677:G(M1) Ganglioside; C018835:asialo GM1 ganglioside; D007371:Interferon-gamma