TFH-derived dopamine accelerates productive synapses in germinal centres by Papa, I, Saliba, D, Ponzoni, M, Bustamante, S, Canete, P, Gonzalez-Figueroa, P, McNamara, H, Valvo, S, Grimbaldeston, M, Sweet, R, Vohra, H, Cockburn, I, Meyer-Hermann, M, Dustin, M, Doglioni, C, Vinuesa, C