The invention relates to novel semaphorins which are distinguished by a particular domain structure and derivatives thereof, nucleic acids (DNA, RNA, cDNA) which code for these semaphorins, and derivatives thereof, and the use thereof.The present invention relates to semaphorins which have a novel, as yet undisclosed and unexpected domain structure and which possess a biochemical function in the immune system (immunomodulating semaphorins). The novel semaphorins are referred to as type L semaphorins (SemaL). They comprise an N-terminal signal peptide, a characteristic Sema domain and, in the C-terminal region of the protein, an immunoglobulin-like domain and a hydrophobic domain which represents a potential transmembrane domain.