SIGLEC1 and infection: The floor of the subcapsular sinus (SCS) in the lymph node is lined by CD169+ macrophages that sample the lymph for antigens, forming an interconnected network overlying the B cell follicle.24,25 Infection and inflammation are associated with disruption of this CD169+ SCS macrophage (SSM) cell layer,26–28 possibly due to their inward displacement into the follicle.26 It has therefore been proposed that SSMs that migrate into the follicle may also differentiate into TBMs.