Interferon-alpha (IFN-alpha) is a multifunctional cytokine that modulates immune response. In spite of the numerous comprehensive studies on the effects of IFN-alpha on various cell types, novel characteristics of this versatile agent emerge continuously. In the present study a differential proteomic approach was used to identify new IFN-alpha-regulated proteins in human primary CD4(+) T cells. Two IFN-alpha-inducible proteins, soluble N-ethylmaleimide-sensitive factor attachment protein alpha (alpha-SNAP) and cleavage stimulation factor-64 (CstF-64) previously not described in this context, were identified. Additionally, several proteins already known as IFN-stimulated genes were observed. The results of proteomics experiments were further studied at the mRNA level using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Both peripheral blood and cord blood CD4(+) T cells were used in order to see if there are differences in IFN-alpha response between these populations. Differences were observed between the IFN-alpha-induced expression kinetics in peripheral blood and cord blood transcripts. The induction was more rapid in peripheral blood than in cord blood cells. CstF-64 expression was upregulated by IFN-alpha at the protein, but not at the mRNA level.