Interferon-gamma inhibits tumor antigen presentation by epidermal antigen-presenting cells.

Murine I-A+ epidermal antigen-presenting cells (APCs) have been shown to be capable of presenting soluble tumor fragments (TFs), as a source of tumor-associated antigens (TAAs), for primary and secondary tumor immune responses. In this study we investigated whether incubation of epidermal APCs in interferon-gamma (IFN-gamma) modulates their ability to present TAA and whether the effects of IFN-gamma on the presentation of tumor antigen correspond to its effects on alloantigen presentation in both primed and unprimed systems. Our results show that three weekly subcutaneous injections of naive mice with GM-CSF-cultured but not with fresh TAA-pulsed epidermal APCs induce protective tumor immunity in naive mice and that the immunostimulatory effect of GM-CSF in this system is abrogated by coculture of epidermal cells in IFN-gamma. Furthermore, epidermal APCs are able to present TAA to primed, tumor-immune mice, as assessed by the elicitation of tumor-specific delayed-type hypersensitivity after injection of TAA-pulsed epidermal APCs. IFN-gamma was found to inhibit tumor antigen presentation by freshly prepared epidermal APCs in this system. The effects of IFN-gamma on the presentation of tumor antigen correlated well with its effects on the primary and secondary mixed epidermal cell-lymphocyte reaction, indicating that IFN-gamma differentially modulates the function of epidermal APCs with regard to induction versus elicitation of immunity.

Interleukin 1 alpha but not transforming growth factor beta inhibits tumor antigen presentation by epidermal antigen-presenting cells.

Cutaneous I-A+ Langerhans cells are the principal antigen-presenting cells within the epidermis, capable of both initiating and eliciting CD4-dependent immune reactions. We recently demonstrated that epidermal Langerhans cells can present tumor-associated antigens and thus may be important in cutaneous tumor immunity. Despite the ability of Langerhans cells to present tumor antigens, they generally fail to induce protective tumor immunity against growing tumors in situ. We therefore investigated whether locally produced cytokines may be able to down-regulate the presentation of tumor-associated antigens and alloantigen by epidermal antigen-presenting cells in primed as well as in unprimed systems in vivo and in vitro. Naive syngeneic mice could be successfully immunized against the spindle cell tumor S1509a by injecting them with granulocyte-macrophage colony-stimulating factor-exposed and tumor-associated antigen-pulsed epidermal cells three times at weekly intervals. Co-incubation of epidermal cells in granulocyte-macrophage colony-stimulating factor and interleukin-1 alpha inhibited tumor-antigen presentation by epidermal antigen-presenting cells in this system and also inhibited alloantigen presentation in the primary mixed epidermal cell-lymphocyte reaction. Tumor necrosis factor-alpha appeared to be a significant mediator of the inhibitory effect of interleukin-1 alpha on the ability of epidermal antigen-presenting cells to induce protective tumor immunity, because addition of anti-tumor necrosis factor-alpha antibody abrogated the observed effect of interleukin-1 alpha. However, the effects of interleukin-1 alpha and tumor necrosis factor-alpha differed with regard to presentation of tumor-associated antigens by epidermal antigen-presenting cells in a primed system. Whereas incubation of epidermal cells in interleukin-1 alpha before or after tumor antigen pulse inhibited their ability to elicit a delayed-type hypersensitivity response against S1509a tumor-associated antigens in tumor-immune mice, culture in tumor necrosis factor-alpha significantly enhanced delayed-type hypersensitivity. Again, these in vivo data corresponded well to similar results obtained in vitro using the secondary mixed epidermal cell-lymphocyte reaction. Incubation of epidermal cells in transforming growth factor-beta, which has been shown to down-regulate T-cell-mediated immune responses in other systems, did not suppress tumor immunity in our assays. Thus, interleukin-1 alpha may be an important regulator of Langerhans cell antigen-presenting function, having effects that are partially mediated via interleukin-1 alpha-induced up-regulation of tumor necrosis factor-alpha secretion within the skin.

Effects of immunomodulatory cytokines on the presentation of tumor-associated antigens by epidermal Langerhans cells.

The recognition and presentation of tumor-associated antigens by cutaneous antigen-presenting cells (APC) may play an important role in the establishment of effective defense mechanisms against newly emerging tumors in the skin. Recent data demonstrate the ability of I-A+ epidermal cells (Langerhans cells) to present tumor-associated antigens for the induction of protective tumor immunity and elicitation of delayed-type hypersensitivity against the murine spindle cell tumor, S1509a. Furthermore, the local cytokine microenvironment in the vicinity of a cutaneous neoplasm may regulate the ability of resident epidermal APC to initiate and/or to elicit protective immunity against incipient cutaneous neoplasms. This article summarizes the effects of granulocyte-macrophage/colony-stimulating factor (GM-CSF), interleukin-1 alpha (IL-1 alpha), tumor necrosis factor-alpha (TNF alpha), transforming growth factor-beta (TGF beta), and interferon-gamma (IFN gamma) on the modulation of antigen presentation by epidermal APC. Our data indicate that these cytokines significantly and differentially modify the ability of epidermal cells to present tumor-associated antigens and that their effects differ with regard to induction of primary immunity (sensitization) or elicitation of secondary immune responses.

Tumor antigen presentation by epidermal antigen-presenting cells in the mouse: modulation by granulocyte-macrophage colony-stimulating factor, tumor necrosis factor alpha, and ultraviolet radiation.

I-A+ epidermal antigen-presenting cells (APCs, Langerhans cells) have been shown to present tumor-associated antigens (TAAs) and to induce tumor immunity in vivo. This study examined the effects of ultraviolet radiation (UVR) and the cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor alpha (TNF-alpha) on the ability of epidermal cells (ECs) to induce or to elicit immunity against the murine spindle cell tumor S1509a. Naive syngeneic mice were immunized three times at weekly intervals with ECs that had been cultured in GM-CSF for 18 h and then pulsed with TAA derived from S1509a. This resulted in protective immunity against subsequent tumor challenge, providing a model to study the conditions required for sensitization against TAAs by epidermal APCs. Culture of ECs in GM-CSF was required for induction of significant protective tumor immunity, and UV irradiation or incubation in TNF-alpha for 2 h after GM-CSF incubation abrogated the immunostimulatory effect of GM-CSF. However, unlike UVR, TNF-alpha did not significantly inhibit the induction of immunity when ECs were exposed to TNF-alpha before overnight incubation in GM-CSF, together with GM-CSF, or after pulsing with TAA, and anti-TNF-alpha antibody treatment did not abrogate the effects of UVR on this system. Furthermore, TNF-alpha incubation of ECs augmented their ability to elicit delayed-type hypersensitivity (DTH) and also enhanced elicitation of DTH by GM-CSF-cultured ECs, whereas UV-irradiation reduced it in a dose-dependent fashion. Taken together, these results demonstrate that GM-CSF, TNF-alpha, and UVR are significant regulators of tumor antigen presentation by epidermal APCs and that the effects of the cytokines examined differ with regard to induction or elicitation of immunity.

Tumor antigen presentation by murine epidermal cells.

The ability of epidermal Langerhans cells to present Ag for CD4-dependent immunity is well documented, and it has been hypothesized that Langerhans cells participate in the generation of immunity against incipient epidermal neoplasms by presentation of tumor-associated Ag in situ. This study examined the ability of murine epidermal cells (EC) to present tumor-associated Ag for the induction of in vivo antitumor immunity. Murine epidermal cells were deleted of Thy-1-bearing cells, cultured in 50 U/ml granulocyte-macrophage-CSF for 14 to 18 h, and pulsed with tumor fragments (TF) derived from S1509a-fibrosarcoma cells. These TF-pulsed EC were injected s.c. into syngeneic recipients at weekly intervals for a total of three immunizations and challenged with viable S1509a tumor cells 1 wk after the last immunization. Control animals received TF-pulsed allogeneic EC or EC treated identically but not pulsed with TF. EC that were pulsed with tumor cell fragments were able to induce protective immunity to tumor growth in vivo and to immunize for a significant delayed-type hypersensitivity response to injected tumor cells. The induction of antitumor immunity with TF-pulsed EC was genetically restricted, and culture of EC in granulocyte-macrophage-CSF was required for development of significant immunity. Furthermore, deletion of I-A+ cells by antibody and complement-mediated lysis eliminated the generation of immunity. Thus, I-A+ epidermal cells are capable of presenting S1509a tumor Ag for the generation of protective antitumor immunity in vivo.