Expression of IL-21R protein and mRNA by CLL B cells is up-regulated by CD40 triggering. (A) Western blot analysis of total protein extracts from resting or CD40-activated (a) purified CLL B cells using an anti-IL-21R or an anti-β-actin antibody. (B) RT-PCR analysis of IL-21R and γc mRNA expression on freshly purified or CD40-activated (a) CLL B cells. A negative control (C-) without RNA was also included. Amplification of the same cDNAs with β-actin-specific primers is also shown. (C) Quantitative RT-PCR analysis indicates an increase of IL-21R mRNA in CD40L-activated CLL B cells with respect to resting cells. Data represent fold of increase and were normalized for the expression of RNA polymerase II mRNA as a housekeeping gene.