Kinetic Analysis of Immune Cells in Blood and Chronic Graft-Versus-Host Disease-Affected Tissues After Allogeneic Hematopoietic Cell Transplantation

Inclusion Criteria:

* \* BOTH COHORTS:

  * Documented written informed consent of the participant and/or parent/guardian.

    * Assent from pediatric participants will be documented per institutional policies and practice.
  * Patients who have received allogeneic hematopoietic cell transplant (HCT) regardless of donor type, condition regimen, or GVHD prophylaxis.
  * Age: ≥ 18 years or ≥ 7 years if 30 kg and above
  * Willingness to:

    * Provide blood sample(s), stool, saliva, and buccal mucosa,
    * If applicable: Permit medical record/ clinical laboratory result review

      * COHORT 1:
  * Patients who have received allogeneic hematopoietic cell transplant (HCT) regardless of donor type, condition regimen, or GVHD prophylaxis.

    * COHORT 2:
  * Patients diagnosed with cGVHD at any time-point after allogeneic HCT regardless of donor type, condition regimen, or GVHD prophylaxis.

Exclusion Criteria:

* \* Women of childbearing potential: Pregnant/nursing

  * Individuals with impaired decision-making capacity
  * An employee who is under the direct/ indirect supervision of the PI/ a co-investigator/ the study manager
  * A direct study team member