Evidence for Low to Undetectable Levels of IL-7 in Stromal Cell Supernatants
| . | Concentration of IL-7* . | ||
|---|---|---|---|
| Undetectable . | ≤0.782 ng/mL . | ≥0.782 ng/mL . | |
| LTBMC-B supernatant† | 18/39 | 15/39 | 6/39‡ |
| LTBMC-B extracellular matrix§ | |||
| Neat | 2/3 | 1/3 | 0/3 |
| Concentrated (10-20×) | 4/6 | 2/6 | 0/6 |
| Purified stromal cells∥ | 3/5 | 2/5 | 0/5 |
| . | Concentration of IL-7* . | ||
|---|---|---|---|
| Undetectable . | ≤0.782 ng/mL . | ≥0.782 ng/mL . | |
| LTBMC-B supernatant† | 18/39 | 15/39 | 6/39‡ |
| LTBMC-B extracellular matrix§ | |||
| Neat | 2/3 | 1/3 | 0/3 |
| Concentrated (10-20×) | 4/6 | 2/6 | 0/6 |
| Purified stromal cells∥ | 3/5 | 2/5 | 0/5 |
*Values are the number of cultures/total assayed. Those with undetectable concentration had no activity above background. Some cultures had detectable levels of IL-7 but fell below the level of quantitation (ie, below the linear part of a 4-parameter curve; >0.782 ng/mL). A few cultures contained quantifiable levels of IL-7 (ie, on the linear part of the standard curve).
LTBMC-B cultures were tested 4 to 6 weeks after initiation. Each culture contained 12 mL of medium.
In the six experiments in which IL-7 was quantifiable, the average concentration of IL-7 ± SD was 1.11 ± 0.29 ng/mL.
The IL-7 present in the extracellular matrix on intact LTBMC-B adherent layers was measured after elution of the IL-7 by treatment with 0.6 mol/L NaCl. In some experiments, the eluted material was concentrated with a 10,000 molecular weight cut-off microconcentrator and the amount of IL-7 present in the retentate was determined by ELISA. IL-7 was not detected in the filtrate.
∥The conditioned media from 104 FACS-purified stromal cells from LTBMC-B of young (1 month old) marrow was collected after 72 hours of culture and the amount of IL-7 was measured by ELISA.