Peptides (P) derived from the alpha -isoform of survivin (Sa) for use as antigen in prophylactic or therapeutic vaccination； and for diagnosis, prognosis or therapeutic monitoring of cancer. (P) comprise (a) 13-18 consecutive amino acids (aa) between positions 17 and 34 of Sa； (b) 13-30 consecutive aa between positions 84 and 113； (c) 13-21 aa between positions 122 and 142, or (d) variants of (a)-(c). All P have binding activity, to at least one HLA-II molecule preponderant in Caucasians, of below 1000 nM and can induce CD4 +>； T lymphocytes specific for survivin. Independent claims are included for the following: (1) polyepitopic fragment (X) comprising the concatenation of at least two epitopes, same or different, at least one being a P, for use as antigen as above； (2) fusion protein (FP) containing a protein (or fragment) fused to P or X, for use as antigen as above； (3) lipopeptide (LP) obtained by adding a lipid to the alpha -amino or reactive sidechains of P or X, for use as antigen as above； (4) expression vector that contains a polynucleotide encoding P, X or LP, under control of appropriate regulators, for use as antigen as above； (5) immunogenic or vaccinating composition containing at least one P, X, FP, LP, vector of (4) plus vehicle, carrier or adjuvant； (6) method for diagnosis, prognosis or monitoring of cancer by contacting, in vitro, a patient sample with P and detecting CD4 +>； T cells specific for survivin； (7) method for selecting CD4 +>； T cells specific for survivin by contacting, in vitro, a cell sample with labeled multimeric complex formed between HLA-II molecule and at least one P, then isolating cells that have bound the complex； (8) P as new compounds, except for the peptide containing aa 89-101 of alpha -survivin； (9) (X), FP and LP as new compounds； (10) new polynucleotides that encode P, X and FP； (11) the vector of (4) as new； and (12) host cells modified by the nucleic acid/vectors of (11) and (12). ACTIVITY : Cytostatic. No d
