X-24 plasmacytoma cell line.

X-24 plasmacytoma cell line does not express the CD40 molecule. Data are representative of 3 independent experiments. (A) The X-24 cell line (upper row) was negative for expression of CD40 mRNA as assessed by reverse transcription–PCR analysis. The amplification of the β-actin shows the integrity of reverse-transcribed RNA (lower row). (B) Exponentially growing X-24 murine plasmacytoma cells were negative for CD40 molecule expression as measured by staining with the anti-CD40–FITC (clone HM40-3)–conjugated mAb (upper panels, solid lines) or the anti-CD40–PE (clone 3/23)–conjugated mAb (lower panels, solid lines). Dashed lines represent the profile of the isotype-matched antibody. (C) Expression of CD40 by X-24 cells was not significantly enhanced by exposure to transgenic CD40L as assessed by coculture for 24 hours with either CL7.1/mCD40L or CL7.1/neo fibroblasts.