The effect of 2-acetyl-4-tetrahydroxybutylimidazole on lymphocyte subsets during a contact hypersensitivity response in the NOD mouse.

The compound 2-acetyl-4-tetrahydroxybutylimidazole (THI) is known to suppress a contact hypersensitivity (CH) response. The effect of THI on lymphocyte subsets during treatment and in a CH response has not been shown in mice. To further define the immunosuppressive potential of THI, a time-course study during the CH response to oxazolone (OX) was performed. While THI can prevent the induction of CH, if treatment is started before sensitization, it has a low therapeutic capability since it could not significantly inhibit the response when continuous oral treatment was commenced during the course of CH. We report that during this response continuous oral treatment of non-obese diabetic (NOD) mice with THI reduced the number of CD4+ and CD8+ T cells in the peripheral blood. In the draining lymph nodes THI treatment had no effect on lymphocyte subsets prior to contact sensitization, but subsequent sensitization and elicitation with OX could not stimulate a significant increase in the number of CD4+ T cells in the treated mice, whereas untreated control mice showed elevated numbers of these lymphocytes. These findings suggest that THI can inhibit an CH response by preventing the recruitment of CD4+ T cells in the draining lymph nodes through an unknown mechanism.

Natural killer cell activity against cultured melanoma cells: a dye-reduction technique with studies on augmented activity by interferon subtypes.

We assessed natural killer (NK) cell activity against cultured melanoma cells using a novel method, with observations on the comparative effects of interferons (IFNs) in NK-stimulating and anti-proliferative assays. Since the tumour cells tested were adherent, a semi-automated colorimetric MTT dye reduction assay was developed to assess NK activity. The three adherent human melanoma cell lines Sk-Mel-28, MM418 and MM96 were shown to be suitable targets for determining NK activity. Also, these were representative of the range of sensitivities of melanoma cells to the anti-proliferative action of type 1 IFNs. The dose-dependent stimulation of NK activity by type 1 IFNs was confirmed in this alternative assay system. IFN-alpha 2b and IFN-beta ser had equivalent stimulatory activities, and IFN-alpha 4 proved less effective, as with assays using the classical K562 system. Augmented NK cytotoxicity did not correlate with anti-proliferative effects of IFN. In anti-proliferative assays, the hierarchy of activity is IFN-beta greater than IFN-alpha 2 greater than IFN-alpha 4, whereas, in the NK augmentation assay IFN-beta and IFN-alpha 2 were of equivalent activity. Interestingly, MM96 was the cell line most resistant to the direct anti-proliferative action of IFN, yet it was the most susceptible of the melanoma cell lines to cytotoxicity by NK cells, whether stimulated or unstimulated by IFN.