Evaluation of antigen-specific immunoglobulin subclass and cytokine production. A, The IgG subclass distribution of PsaA-specific antibodies was determined by ELISA for sera obtained from BALB/c mice at week 5 (following 2 immunizations as outlined in Figure 2). Data are presented as means ± SEM for 5 mice per group. B, For ELISPOT assays, C3H/HeJ mice immunized with the indicated antigens at week 0, and boosted with PsaA alone at week 2. Splenocytes were prepared from individual mice at week 3 were stimulated with soluble PsaA for the evaluation of PsaA-stimulated cytokine secreting cells, or with ELISPOT plate-immobilized PsaA for the enumeration of PsaA-specific antibody secreting cells (ASC). The data for cytokine spots are combined from two experiments with 3 mice per group and the data for ASC are from one experiment with 3 mice per group. Spots from individual mice and group means are shown.