DESCRIPTION

Graft-versus-host disease (GVHD) is a multiorgan inflammatory process that develops when immunologically competent T lymphocytes from a histoincompatible donor are infused into an immunocompromised host unable to reject them; divided into acute and chronic, historically based on time of presentation but best delineated by clinicopathologic findings

• Acute:
  • Develops within 100 days after allogeneic hematopoietic stem cell transplant (HSCT)
  • Affects skin, GI tract, and/or liver
  • Graded from I to IV based on organ involvement, percent of body surface area involved (skin), volume of diarrhea (gut), and/or elevation of serum bilirubin (liver)
• Chronic:
  • Develops 100 days after allogeneic HSCT
  • Presents with diverse features resembling autoimmune syndromes; affects multiple organ systems
  • Chronic subtypes
    • Progressive: extension of acute GVHD
    • Quiescent: after resolution of acute GVHD
    • De novo: no prior acute GVHD

EPIDEMIOLOGY

• Acute GVHD (grades II to IV): 10–80% of patients receiving T-cell–replete HSCT
  • 35–45% for human leukocyte antigen (HLA)–identical related donor bone marrow
  • 60–80% if 1-antigen HLA-mismatched unrelated donor bone marrow or peripheral stem cells
  • 35–65% if 2-antigen HLA-mismatched unrelated umbilical cord blood
• Chronic GVHD: most common cause of late morbidity and mortality of allogeneic HSCT
  • 15–25% if HLA-identical related marrow
  • 40–60% if HLA-matched unrelated marrow
  • 54–70% if HLA-matched unrelated peripheral stem cells
  • 20% if unrelated umbilical cord blood
• Flare-ups triggered by infection (usually viral)

RISK-FACTORS

• HLA disparity (both major and minor antigens)
• Older donor or recipient age
• Stem cell source and dose
  • Highest risk: with peripheral stem cells
  • Lowest risk: with umbilical cord blood
• Donor leukocyte infusions
• Reactivation of viruses (e.g., HHV-6, CMV)
• T-cell depletion decreases incidence.
• Acute GVHD-specific
  • Higher intensity conditioning regimen
  • Prior pregnancies in female donors
  • Use of total body irradiation
• Chronic GVHD specific
  • Severity of acute GVHD
  • Malignancy as indication for transplantation
  • Gender mismatch (female donor, male recipient)
  • Type of immunosuppressive prophylaxis

GENERAL-PREVENTION

• Transfusion: irradiation of all cellular blood products for patients at risk
• Stem cell transplantation
  • Selection of a histocompatible donor
  • Immunosuppression (gold standard): cyclosporine or tacrolimus with a short course of methotrexate
  • Other options: corticosteroids, sirolimus, mycophenolate mofetil, and post-HSCT cyclophosphamide
  • Donor T-cell depletion with anti–T-cell antibodies ex vivo in graft or in vivo in recipient

PATHOPHYSIOLOGY

• Acute GVHD: interaction of donor and host innate and adaptive immune responses
  • Severity related to degree of HLA mismatch
  • Three phases ending in “cytokine storm”
    • Tissue damage by conditioning regimen
    • Priming and activation of donor T cells
    • Infiltration of activated T cells into skin, GI tract, and liver resulting in apoptosis
• Chronic GVHD: findings similar to autoimmune disorders: donor T cells directed against host antigens, donor T-cell alloreactivity, B-cell dysregulation, regulatory T-cell deficiency; marked collagen deposition in target organs and lack of T-cell infiltration

ETIOLOGY

• HSCT
• Transfusion of nonirradiated blood products to immunodeficient hosts: caused by viable donor lymphocytes engrafting in the recipient
• Transfusion of nonirradiated blood from a donor homozygous for one of the recipient’s HLA haplotypes (1st- or 2nd-degree relative)
• Intrauterine maternal–fetal transfusions and exchange transfusions in neonates
• Solid organ grafts: contain immunocompetent T cells, into immunosuppressed recipient