Absence of PLP-specific DTH responses in mice adoptively transferred with MPL-PURO-expressing B cells. (A) Treated and untreated mice in remission were injected with PLP-coupled SRBCs into the front right footpad. The swelling of the injected footpad was compared with the uninjected left footpad 24 and 48 hours later. Each symbol represents one mouse and the horizontal bars represent the mean response of each group. Baseline responses to the antigen challenge alone were measured in unprimed normal control mice. (B) RT-PCR was performed on total RNA extracted from the spleens of mice treated with MPL-PURO-infected B cells and employed in the DTH assays (lanes 1-4). Lanes 6 and 7 are positive and negative control samples prepared from MPL-PURO-infected WEHI-231 B cells and from the spleen of an untreated mouse, respectively. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was amplified in all samples indicating equal level of total RNA usage.