CXCR5 receptor internalization resulting from CXCL13 ligation is followed by a rapid increase of CXCR5 mRNA levels. Surface expression (A) and mRNA levels (B) of CXCR5 on PBMCs incubated with or without CXCL13 over a 24-hour time-course experiment. The surface expression of CXCR5 decreased, despite a rapid increase of CXCR5 mRNA expression already after 30 minutes, in cells cultured with the chemokine CXCL13. At 12 and 24 hours, only minor differences could be detected between the cultures. One representative experiment of 3 is shown.