Inclusion Criteria:  healthy volunteers aged between 18 and 70  volunteers free from lymphoid hemopathy, immune deficiency and autoimmune disease.  3 categories : volunteers between 18 and 34 years of age, volunteers between 35 and 50 years of age, volunteers between 51 and 69 years of age.  Exclusion Criteria:  any recent vaccination (< 4 weeks) tumoral pathology lymphoïd hemopathy immune deficiency autoimmune disease transplanted patients inflammatory / systemic diseases hypersensitivity or allergies  treatments likely to modify the immune response :  calcineurin inhibitors: ciclosporin, tacrolimus -antimetabolite: azathioprine, mycophenolate mofetil / mycophenolic acid, 6-mercaptopurine, methotrexate cyclophosphamide antilymphocyte serum (rabbit, horse) mTOR inhibitors: everolimus, sirolimus anti-CD25 (anti IL2-R): basiliximab, dacliximab -belatacept (anti CD80-86) abatacept (CTLA4-Ig) OKT3 (Muronomab-CD3, anti-CD23) glucocorticoids: methylprednisolone, prednisone, prednisolone. entuzumab (anti-CD52) rituximab, ocrelizumab (anti-CD20) eculizumab (anti-C5) anakinra (analogue IL1-RA) leflunomide (dihydroorotate dehydrogenase inhibition) bortezomib (proteasome inhibitor) fingolimod (S1P receptor antagonist) alentuzumab (anti CD52) Ig G -antiTNF (etanercept, infliximab, adalimumab, certolizumab) vedolizumab (Anti-integrin α4β7 Ab) ustekinumab (anti-IL12) natalizumab (anti-integrin a4) mitoxantrone (topoisomerase type II inhibitor) tocilizumab (anti-IL6)