If you are found to be eligible to take part in this study, you will receive one injection of IL-11 under the skin (usually of the arms, legs or abdomen) 3 times a week. If your platelet count increases, treatment will continue on this schedule as long as a platelet increase is observed. If the treatment is well tolerated but there is not enough of a platelet improvement, the dose and frequency of IL-11 injections may be increased. If the platelet count becomes high enough, treatment may be stopped but may also be restarted if necessary.