IL12-mediated sensitizing of T-cell receptor-dependent and -independent tumor cell killing.

Interleukin 12 (IL12) is a key inflammatory cytokine critically influencing Th1/Tc1-T-cell responses at the time of initial antigen encounter. Therefore, it may be exploited for cancer immunotherapy. Here, we investigated how IL12, and other inflammatory cytokines, shape effector functions of human T-cells. Using a defined culture system, we followed the gradual differentiation and function of antigen-specific CD8(+) T cells from their initial activation as naïve T cells through their expansion phase as early memory cells to full differentiation as clonally expanded effector T cells. The addition of IL12 8 days after the initial priming event initiated two mechanistically separate events: First, IL12 sensitized the T-cell receptor (TCR) for antigen-specific activation, leading to an approximately 10-fold increase in peptide sensitivity and, in consequence, enhanced tumor cell killing. Secondly, IL12 enabled TCR/HLA-independent activation and cytotoxicity: this "non-specific" effect was mediated by the NK cell receptor DNAM1 (CD226) and dependent on ligand expression of the target cells. This IL12 regulated, DNAM1-mediated killing is dependent on src-kinases as well as on PTPRC (CD45) activity. Thus, besides enhancing TCR-mediated activation, we here identified for the first time a second IL12 mediated mechanism leading to activation of a receptor-dependent killing pathway via DNAM1.

Fulminant skin GvHD with a cytokine pattern resemblant of cytokine release syndrome successfully treated with multimodal immunosuppression including tocilizumab.

Acute Graft-versus-Host-Disease (GvHD) is a potentially life-threatening complication after allogeneic stem cell transplantation. If not treated early and adequately, the complex immunological mechanisms may lead to a self-perpetuating cycle of alloreactivity, which is then associated with a high mortality. Here we assessed the cytokine profile on a daily basis in a patient with grade 4 skin GvHD, demonstrating a signature resembling cytokine-release-syndrome. After multimodal immunosuppressive intervention, including treatment with the IL6 receptor-blocking antibody tocilizumab, the severe clinical symptoms unexpectedly resolved within 48 hr.

Src-kinase inhibitors sensitize human cells of myeloid origin to Toll-like-receptor-induced interleukin 12 synthesis.

Src-kinase inhibitors hold great potential as targeted therapy against malignant cells. However, such inhibitors may also affect nonmalignant cells and cause pronounced off-target effects. We investigated the role of the dual kinase inhibitor dasatinib on human myeloid cells. Dasatinib is clinically used for the treatment of bcr/abl⁺ leukemias because it blocks the mutated tyrosine kinase abl. To understand its effect on the development of antigen-specific T-cell responses, we assessed antigen-specific priming of human, naïve T cells. In surprising contrast to the direct inhibition of T-cell activation by dasatinib, pretreatment of maturing dendritic cells (DCs) with dasatinib strongly enhanced their stimulatory activity. This effect strictly depended on the activating DC stimulus and led to enhanced interleukin 12 (IL-12) production and T-cell responses of higher functional avidity. Src-kinase inhibitors, and not conventional tyrosine kinase inhibitors, increased IL-12 production in several cell types of myeloid origin, such as monocytes and classical or nonclassical DCs. Interestingly, only human cells, but not mouse or macaques DCs, were affected. These data highlight the potential immunostimulatory capacity of a group of novel drugs, src-kinase inhibitors, thereby opening new opportunities for chemoimmunotherapy. These data also provide evidence for a regulatory role of src kinases in the activation of myeloid cells.