Short-term and long-term engraftment at different adhesion times.

Fresh male marrow suspensions were inoculated onto pre-established female stromal layers and allowed to adhere for 20 minutes (0.3 hours), 40 minutes (0.7 hours), 1 hour, 6 hours, or 24 hours before being harvested for transplantation. The 6-hour and 24-hour adhesion times were performed only for long-term engraftment. Recipient bone marrow was analyzed 2 weeks later for short-term engraftment and 8 to 11 weeks later for long-term engraftment. The ratios of actual to expected engraftment are shown. Results of 4 experiments are shown, with 3 to 5 recipients per group per experiment. ░, short-term engraftment; ▪, long-term engraftment. *For short-term engraftment, the result for 20-minute group is significantly lower than for the 1-hour (P = .014), but there is no significant difference between the 20-minute and 40-minute groups or between the 40-minute and 1-hour groups. For long-term engraftment, the 1-, 6-, and 24-hour groups are not significantly different from each other. The 20-minute and 40-minute groups are not significantly different from each other, but **both are significantly lower than for the 1-, 6-, and 24-hour groups (P < .0006).