B220-negative plasma cells display a unique chemokine receptor mRNA expression profile. (A) mRNA expression for CCR4, CCR7, CXCR5, D6, and CXCR4 by B220-negative plasma cells from E/P^-/- cervical lymph nodes and wild-type IgM⁺ B cells was determined by RT-PCR. The presence or absence of reverse transcriptase (RT) in the RT-PCR reactions is indicated. (B) Semiquantitative RT-PCR using 2-fold serial dilutions of input cDNA was used to determine the relative expression of CCR9, CCR3, and CXCR2 for plasma cells and IgM⁺ B cells. CXCR4 was included as a control for each cell type. WT whole spleen cells were used as a positive control for all genes in panels A and B. The complete mRNA expression profile of chemokine receptors examined is shown in Table 2. The results are representative of 4 plasma cell and 6 IgM⁺ B-cell isolations.