Stromal cell control of conventional and ectopic germinal centre reactions.

• Stromal cells support the initiation, maintenance and output of germinal centre responses.• Fibroblasts are key mediators of tertiary lymphoid structure assembly in non-lymphoid tissues.• Activated lung resident fibroblasts mediate lymphocyte recruitment for ectopic germinal centre formation.• Follicular-like stroma can support cross-reactive germinal centres in the lung.