Variable HLA expression on deceased donor lymphocytes: Not all crossmatches are created equal

Area of Science:

• Immunology
• Transplantation Science
• Cell Biology

Background:

• Flow cytometric crossmatch tests are vital for detecting donor-specific antibodies and assessing transplant eligibility.
• Crossmatch sensitivity relies heavily on the quality of lymphocytes, specifically human leukocyte antigen (HLA) expression on their surface.

Purpose of the Study:

• To investigate the impact of HLA expression variability on crossmatch reactivity.
• To compare HLA expression across different donor types (deceased donor vs. living donor) and tissue sources (blood, spleen, lymph nodes).

Main Methods:

• Isolation of lymphocytes from various donor types and tissues.
• Flow cytometry analysis to quantify HLA class I and class II expression on B and T cells.
• Comparison of HLA expression levels and their correlation with crossmatch outcomes.

Main Results:

• HLA class I expression was significantly lower on B cells from deceased donor blood compared to other tissues (p = 0.0004).
• Living donor blood exhibited higher HLA class II on B cells and class I on T cells than deceased donor tissues.
• Spleen demonstrated the highest expression of HLA class II on B cells and class I on T cells among deceased donor tissues.
• Memory (CD27+) status affected HLA expression on B cells, but not T cells.
• Differences in HLA expression between tissues from the same donor influenced crossmatch results.

Conclusions:

• HLA expression on lymphocytes is influenced by donor type, tissue source, and cell type (B vs. T, memory vs. non-memory).
• Variability in HLA expression significantly impacts flow cytometric crossmatch outcomes.
• Routine monitoring of HLA expression is recommended to ensure crossmatch sensitivity and reconcile results with antibody analyses.