Inclusion Criteria:

- Patients must have reached their 18th birthday

- Women of childbearing potential must agree to use effective methods of contraception

- Patients must be affiliated to a social security regime

- Patients must have received imatinib therapy for at least 36 months.

- Patients must be in complete molecular remission during at least two consecutive
years with at least five RT-PCR negative measures for bcr-abl transcripts.

- Patients must be HIV, HCV and HBV negatives

- Patients who have molecular follow-up realized in accordance with international
recommendations

- All patients must be informed of the investigational nature of this study and must
sign and give written informed consent.

Exclusion Criteria:

- Patients who are protected by the law. Patients who are unable to give their consent
to participate to the study.

- Patients who have pathologies or treatments that are able to enhance the potential
relapse risk after stopping imatinib. Patients who have pathologies or treatments
which able to interfere with immunologic study (excepted IFN α):

Corticosteroids or other immuno suppressors Other concomitant malign pathology treated by
chemotherapy or radiotherapy Previous or programmed Haematopoietic Stem Cell allogreffe