Cell Therapy With Treg Cells Obtained From Thymic Tissue (thyTreg) to Prevent Rejection in Heart Transplant Children

Inclusion Criteria: 1. Patient under two years of age, who meets all the necessary requirements to undergo a heart transplant. 2. Patients without contraindication to immunosuppressive drugs. 3. Parents and/or guardians must be willing and able to understand the purpose and risks of the study and must sign the informed consent document Exclusion Criteria: 1. Patients with DiGeorge Syndrome, since their thymic function is affected. 2. Human immunodeficiency virus positive serology 3. Epstein-Barr virus active infection 4. Patients hyperimmunized with cytotoxic anti-human leukocyte antigen antibodies 5. Patients with a history of previous malignancy 6. Patients who have participated in other intervention studies in the last month. 7. Patients who have received induction therapy with Basiliximab or Thymoglobulin. 8. Patients who have previously been thymectomized or transplanted. 9. Patients who have been diagnosed with severe autoimmune disease (celiac disease, autoimmune hypothyroidism, autoimmune diabetes) 10. Patients who will receive an asystole heart