Synergistic enhancement of cell-mediated immunity by interleukin-12 plus interleukin-2: basis for therapy of cutaneous T cell lymphoma.

Cutaneous T cell lymphoma is a clonally derived, skin-invasive malignancy of CD4+ T lymphocytes with the phenotype of mature helper T cells. Previous work has demonstrated that the Sézary form, or typically leukemic form of cutaneous T cell lymphoma, is characterized by prominent immunologic defects, including depressed cell-mediated immunity associated with marked defects in the production of interleukin-12 and other type 1 helper T cell cytokines. Recent clinical trials with recombinant human interleukin-12 for cutaneous T cell lymphoma have demonstrated that it is a potent therapeutic agent, which induces cytotoxic T cell responses. Nevertheless, a high rate of refractoriness to recombinant human interleukin-12 occurred in these studies that may be related to the downmodulation of interleukin-12 receptor expression by chronic interleukin-12 use. In an effort to enhance the overall response rate and to overcome the refractoriness to recombinant human interleukin-12 therapy, we studied the immunologic effects in vitro of adding interleukin-2 to interleukin-12 as a model to achieve these goals. We examined the stimulation of interferon-gamma production, natural killer cell activity and interleukin-12 receptor expression by T cells of cutaneous T cell lymphoma patients. The addition of interleukin-12 to cutaneous T cell lymphoma patient peripheral blood cells resulted in the production of interferon-gamma (mean = 7914 pg per ml +/- 2161, n = 15) as did interleukin-2 alone (mean = 7222 pg per ml +/- 2228, n = 15). Importantly, the addition of interleukin-2 to the interleukin-12 synergistically enhanced the levels of interferon-gamma produced (mean = 16 792 pg per ml +/- 2492 n = 15) (p <0.01). Similarly, addition of interleukin-2 to interleukin-12 synergistically enhanced both the natural killer cell activity of 15 cutaneous T cell lymphoma patients as well as T cell surface interleukin-12 receptor expression in comparison with the effects of interleukin-12 or interleukin-2 alone. Thus, interleukin-2 plus interleukin-12 unequivocally produces the synergistic enhancement of multiple parameters of cell-mediated immunity as well as upmodulating interleukin-12 receptor expression; this indicates that protocols combining these two potent immune enhancing cytokines may have added therapeutic benefit for cutaneous T cell lymphoma.

Sézary syndrome patients demonstrate a defect in dendritic cell populations: effects of CD40 ligand and treatment with GM-CSF on dendritic cell numbers and the production of cytokines.

Sézary syndrome (SzS) is an advanced form of cutaneous T-cell lymphoma associated with involvement of the peripheral blood by malignant T cells. The disease is defined by impaired cell-mediated immunity and the production of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2), possibly as a result of deficient IL-12 production. To understand the mechanism of this impairment, we examined the composition and function of dendritic cells and monocytes in the blood of SzS patients with different levels of peripheral blood tumor burden. Consistent with our previous observations, numbers of monocytes in SzS patients were comparable to numbers observed in healthy donors. In contrast, decreased IL-12 production correlated with a decrease in the numbers of CD11c(+) dendritic cells, which was particularly profound among patients with medium (20%-50% circulating malignant T cells) and high (more than 50% circulating malignant T cells) tumor burden. Furthermore, CD123(+) dendritic cells, major producers of IFN-alpha, were significantly diminished in SzS patients, regardless of the level of tumor burden. Granulocyte macrophage-colony-stimulating factor-treated patients experienced an increase in the number of dendritic cells but not in IFN-alpha or IL-12 production. However, in vitro stimulation of peripheral blood mononuclear cells from SzS patients with rCD40L and IFN-gamma significantly increased the production of IL-12. Thus, our results demonstrate a profound defect in circulating dendritic cells in SzS patients that may contribute to the pathogenesis of the cytokine disorders and to the depressed cellular immunity. Importantly, the ability of rCD40L to potently induce IL-12 production from monocytes and residual dendritic cells of SzS patients could potentially serve as an immune-restorative therapeutic agent.