UNIT 4: TISSUE AND ORGAN TRANSPLANT SERVICES

The AATB (American Association of Tissue Banks

Org that oversees tissue transplant activities in the US

How soon after death must tissue recovery occur

within 24 hours

what is an autograph

A graph implanted back into the same person it was taken from

What is an allograph

A graph transferred between two members of the same species

What is a xenograph

Graft transferred between different species

How many oragns can typically be recovered from 1 donor

4-5 organs

How many recipients may benefit from one deceased tissue donor

50-100 recipients

What are the most frequently transplanted tissues

Bone and corneas

Why do corneal grafts generally have low rejection risk

Because the cornea has little blood exposure (low vascularization)

What is the source of autologous bone grafts

The patients own iliac crest

Advantage of cadaver bone allographs over autographs

No need for a second surgery, less pain

Can tissue transplants transmit disease

Yes, though rare —> Rabies, CDJ, HIV, Hep B/C,

What testing became required for tissue donors in 2005

NAT testing for HIV and HCV RNA

Are HLA and ABO matching usually required for tissue grafts

No, Rarely

Why should transfusions around transplant surgery be leukocyte-reduced

To minimize development of HLA antibodies

Define “passenger lymphocytes”

Donor lymphocytes transferred within a transplanted organ

Define microchimerism

Coexistence of donor and recipient lymphocytes in the host’s circulation.

One benefit of microchimerism

Promotes tolerance, improves graft longevity

One risk of microchimerism

Donor lymphocytes can cause GVHD

What medication is commonly given to prevent graft rejection

Cyclosporin (immunosuppressant)

Persistent donor lymphocytes can cause

• GVHD

• Hemolytic anemia

• Production of antibodies against recipient RBC antigens → hemolysis

What test helps diagnose hemolytic anemia post-transplant

DAT

Which organs are most associated with GVHD-related hemolysis

Organs rich in lymphoid tissue, especially the liver

Why is GVHD not a concern in autologous bone marrow transplants

Because the marrow comes from the recipient, so no foreign lymphocytes are introduced

DAT vs IAT

DAT: Detects antibodies/complement attached to patients RBCS

IAT: Detects antibodies floating in patient serum/plasma (ALLO-ANTIBODIES)

Corneal Grafts

• First human allografts ever performed.

• Obtained from deceased donors.

• Used to replace opaque or diseased corneas and restore vision.

• Corneas are typically not at high risk for rejection because they have minimal blood exposure.