Dados do Trabalho

Título

IT TAKES TWO TO TANGO: COMBINED HLA-DPA/B CHAIN ANTIBODY REACTIVITY IN A KIDNEY TRANSPLANTED PATIENT.

Introdução

A 60 years-old male with a previous renal transplant re-entered the deceased donor waitlist and was offered a second kidney transplant. Serum reactivity in the single antigen bead (SAB) assay showed positivity with 2/3 HLA-DP18 and DP28 beads, thus, no identified eplet could explain the reactivity.

Relato do Caso

Patient HLA typing, HLA-A*03,*11; B*35; DRB1*11,*12, was performed by rSSO (LabType™ SSO, One Lambda Inc), as well as first donor, HLA-A*02,*03; B*35,*57; C*04,*06; DRB1*07,*10; DQB1*03(9),*05. The second donor typing was performed by NGS (One Lambda™ AllType FASTplex): HLA-A*01:01,*03:01; B*07:02,*08:01; C*07:01,*07:02; DRB1*03:01,*15:01; DRB3*01:01; DRB5*01:01; DQB1*02:01,*06:02; DQA1*01:02,*05:01; DPB*01:01,*02:01; DPA1*01:03,*02:01. Although the HLA-DPB1*02:01 specific antibody appeared to be directed against the second donor DP allele, justified by the 84GGPM eplet (DPB1*02:01, DPB1*02:02, DPB1*04:01, DPB1*04:02, DPB1*23:01, DPB1*105:01), the remaining DP specific reactivity couldn't be explained.
In order to characterize serum HLA-DP antibody reactivity, absorption with x-match cells and elution (AXE) technique was performed with surrogate donor leukocytes expressing DPB1*01:01,*04:01; DPA1*01:03,*02:01.

Resultados

The results of SAB eluate demonstrated that the surrogate donor DPB1*04:01-DPA1*01:03 heterodimer was able to adsorb out the entire reactivity found in the classical SAB test. HLA sequence alignment allowed us to identify the alpha/beta chain eplet pair responsible for the entire reactivity identified in both sera and eluate.

Discussão e Conclusões

This case demonstrates that the epitope list within the epitope registry is incomplete and additional methods, such us AXE assay and sequence alignment, are essential to characterize the true reactivity found in the SAB assay.

Palavras Chave

HLA antibodies, Single-antigen bead assays, Adsorption-elution