In addition to the other answers, antigen naive (i.e. never-before activated) B and T cells circulate constantly between lymph nodes and blood. This maximises the chances of B and T cells finding their antigen and responding, even if the antigen is only found in those lymph nodes nearest to the infection.
The-very-naughtyduck t1_ixc39wm wrote
Reply to Why do immune reactions take place in the lymph nodes closest to the site of infection? by arlomurfett
In addition to the other answers, antigen naive (i.e. never-before activated) B and T cells circulate constantly between lymph nodes and blood. This maximises the chances of B and T cells finding their antigen and responding, even if the antigen is only found in those lymph nodes nearest to the infection.