A ligand includes each of the complementary-determining regions (CDRs) set forth in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3 SEQ ID No. 4, SEQ ID No. 5 and SEQ ID No. 6 or any sequence having either number of substituted aminoacids within said sequences as indicated in the following, from 0 to 3 in CDR1 (SEQ ID No.1), from 0 to 2 in CDR2 (SEQ ID No.2), from 0 to 2 in CDR3 (SEQ ID No.3), from 0 to 1 in CDR4 (SEQ ID No.4), from 0 to 4 in CDR5 (SEQ ID No.5), from 0 to 2 in CDR6 (SEQ ID No.6), or aminoacids substituted with other aminoacids having equivalent chemical functions and properties, within said sequences SEQ ID No. 1 to SEQ ID No. 6.