FIG. 2.
B. bigemina RAP-1 CT-1-specific T cells respond to aa 418 to 480. Three CT-1-specific Th cell clones (A to C) and one RAP-1-specific Th cell clone specific for an epitope within aa 144 to 187 (D) were cultured in a 3-day proliferation assay with autologous APC, 2 U of recombinant human IL-2 per ml, and 1, 5, or 25 μg of recombinant MBP fusion proteins per ml, consisting of the whole RAP-1 protein (closed circles), the N terminal fragment of CT-1 (CT-1N) consisting of aa 386 to 448 (closed triangles), the C-terminal fragment of CT-1 (CT-1C) consisting of aa 418 to 480 (open triangles), or control MBP protein (open circles). Cells were radiolabeled for 6 h with [3H]thymidine, harvested, and counted. The results are presented as the mean ± range of variation around the mean of duplicate cultures. Background proliferative responses of cells in medium plus IL-2 for the clones were as follows: 2216.2B2, 15,305 ± 639 cpm; 2216.1G8, 12,652 ± 2,376 cpm; 2234.1E3, 12,635 ± 775 cpm; and 2216.1H4, 16,353 ± 3,758 cpm.