TABLE 5.
Sensitivity of the ELISPOT assaya
| Plated cells/well | No. of expected spots/well | No. of counted spots/well | Frequency of IFN-γ-producing cells |
|---|---|---|---|
| CTL alone (100) | 33 | 33 | 1/3 |
| PBL alone (105) | 0 | 0 | <1/100,000 |
| PBL (105) + CTL (100) | 33 | 32 | 1/3,128 |
| PBL (105) + CTL (50) | 16 | 16 | 1/6,253 |
| PBL (105) + CTL (25) | 8 | 9 | 1/11,113 |
| PBL (105) + CTL (5) | 1 | 1 | 1/100,000 |
| PBL (105) + CTL (3) | 1 | 1 | 1/100,000 |
a
CTL line 1520 (gp100 peptide specific) was used in titration experiments. This line was pretested in ELISPOT for the frequency of IFN-γ-producing T cells in response to gp100 peptide on the day preceding the titration experiment. The frequency was 1/3. Decreasing numbers of CTL were mixed with normal nonactivated PBL (105/well), and ELISPOT assays were performed, using the gp100 peptide (1 μg/ml) for T-cell stimulation in triplicate wells. Results are from one of two titration experiments performed.