Proteins, nucleic acids, and antibodies BTNL9 and uses thereof

A soluble multimeric protein BTNL9 comprising (a) a polypeptide having an amino acid sequence identical by at least 90% at 35- 257 amino acids of SEQ ID NO: 2, and (b) a second polypeptide having a sequence identical at least 90% to amino acids 35-257 of SEQ ID NO: 2, amino acids in which the window of alignment of the amino acid sequences of the polypeptides of (a) and (b) with amino acids 35-257 SEQ ID NO: 2 is at least 80 amino acids long. wherein (i) the protein BTNL9 multimeric is at least one tetramer and / or (ii) the protein BTNL9 multimeric has a molecular weight four times greater than that of a polypeptide of (a), and wherein the protein BTNL9 multimeric it can inhibit the proliferation of a T cell stimulated by anti-CD3 antibody.