The vanous embodiments relate to peptide antagonists of yc-family cytokines, lnterleukin-2 (IL-2), lnterleukin-4 (IL-4), lnterieukin-7 (IL-7), lnterleukin-9 (IL-9), lnterteukin-15 (IL-15), and lnterteukin-21 (IL-21 ). The yc-cytokines are associated with important human diseases, such as leukemia, autoimmune diseases, collagen diseases, diabetes mellitus, skin diseases, degenerative neuronal diseases and graft-versus-host disease (GvHD). Thus, inhibitors of yc-cytokine activity are valuable therapeutic and cosmetic agents as well as research tools. Traditional approaches to inhibiting yc-cytokine activity involve raising neutralizing antibodies against each individual yc-cytokine family member/ receptor subunit. However, success has been limited and often multiple yc-cytokine family members co-operate to cause the disease state. Combinatorial use of neutralizing antibodies raised against each factor is impractical and poses an increased risk of adverse immune reactions. The present embodiments overcome these shortcomings by utilizing peptide antagonists based on the consensus yc-subunit binding site to inhibit yc-cytokine activity.Les différents modes de réalisation de la présente invention ont pour objet des antagonistes peptidiques des cytokines de la famille γc, l'Interleukine-2 (IL-2), l'Interleukine-4 (IL-4), l'Interleukine-7 (IL-7), l'Interleukine-9 (IL-9), l'Interleukine-15 (IL-15) et l'Interleukine-21 (IL-21). Les cytokines γc sont associées à d'importantes maladies humaines, telles que la leucémie, les maladies auto-immunes, les maladies du collagène, le diabète sucré, les maladies cutanées, les maladies neuronales dégénératives et la réaction du greffon contre l'hôte (GvHD). Ainsi, les inhibiteurs de l'activité des cytokines γc sont des agents thérapeutiques et cosmétiques de valeur ainsi que des outils de recherche. Des approches traditionnelles de l'inhibition de l'activité des cytokines γc consistent à dresser des anticorps neutralisants contre chaque m
