Figure 4.

Blood leukocytes from immunized mice respond to antigen in the presence of T cell help. Leukocytes were purified from the pooled blood or spleen of six mice immunized 14 d previously with NP-KLH. 10⁷ of these cells were transferred to mice previously primed with a single injection of HSA in alum. Recipients were either left untreated or boosted with NP-HSA as indicated. 4 d after transfer, recipients were killed and the frequency of NP-specific IgG1 ASCs determined in bone marrow or spleen are indicated. The horizontal bar shows the average for each condition. The resolution of this assay was 0.1 IgG1 ASCs per 10⁶ plated cells. The number of recipients assessed for each condition is indicated. No NP- specific IgG1 ASCs were detected in either the absence of transferred cells or after transfer of leukocytes from naive mice (not depicted).