You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["RNA", "CellLine", "Protein", "DNA", "CellType"].

Please return the output as a JSON object of the format: {"DNA" : ["TAL1", ...], "RNA": ["mRNAs", ...], "CellLine": ["T cells", ...], "CellType": ["monocytes", ...], "Protein": ["IL-2", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

T cell-specific negative regulation of transcription of the human cytokine IL-4. IL-4 secreted by activated T cells is a pleiotropic cytokine affecting growth and differentiation of diverse cell types such as T cells, B cells, and mast cells. We investigated the upstream regulatory elements of the human IL-4 promoter. A novel T cell-specific negative regulatory element (NRE) composed of two protein-binding sites were mapped in the 5' flanking region of the IL-4 gene:-311CTCCCTTCT-303 (NRE-I) and-288CTTTTTGCTT-TGC-300 (NRE-II). A T cell-specific protein Neg-1 and a ubiquitous protein Neg-2 binding to NRE-I and NRE-II, respectively, were identified. Furthermore, a positive regulatory element was found 45 bp downstream of the NRE. The enhancer activity of the PRE was completely suppressed when the NRE was present. These data suggest that IL-4 promoter activity is normally down-regulated by an NRE via repression of the enhancer positive regulatory element. These data may have implications for the stringent control of IL-4 expression in T cells.
{"CellLine": [], "CellType": ["activated T cells", "mast cells", "B cells", "T cells"], "DNA": ["NRE - I", "PRE", "NRE", "IL - 4 promoter", "upstream regulatory elements", "IL - 4 gene", "human IL - 4 promoter", "positive regulatory element", "45 bp downstream", "novel T cell - specific negative regulatory element", "NRE - II", "enhancer positive regulatory element"], "Protein": ["Neg - 2", "IL - 4", "ubiquitous protein", "pleiotropic cytokine", "Neg - 1", "human cytokine IL - 4", "T cell - specific protein"], "RNA": []}