Date: Saturday, June 1, 2019
Session Time: 5:30pm-7:30pm
Presentation Time: 5:30pm-7:30pm
Location: Hall C & D
*Purpose: To determine the detection rate of IgG subclasses (IgGsc) and C3d-binding HLA-antibodies (abs) in a cohort of highly sensitized kidney transplant patients.
*Methods: We evaluated, in cryopreserved sera from 90 potential renal transplant recipients, HLA-abs Class I and Class II using single antigen beads (SAB). C3d was detected by Luminex (Lifecodes®), IgG 1-4 subclasses were evaluated using monoclonal abs for each IgGsc (Luminex).
*Results: The SAB were able to reveal 1,684 abs, additionally 63 were only detected by C3d assay and 24 by IgGsc (n=1771).The IgGsc assay showed 367 abs with at least one IgGsc, the most common was IgG1 alone or associated with other subclasses (351, 75.6%); only 7 IgG2 and 9 IgG3 were found isolated form IgG1. IgG4 was identified in 17 abs, always in combination with IgG1. A MFI >4000 of the HLA-SAB was directly related with the detection of one or more IgGsc (*p=<0.001). Figure 1.The C3d assay exposed 216 complement-binding abs; 128 of these were identified in the IgGsc as well. Table 1 depict a more detailed analysis of each Class I and Class II category, its IgG detection and C3d-binding capacity.A multivariate analysis using different models showed that the best predictors of IgGsc detection were: finding an HLA-DQ ab and the positivity of the C3d assay (OR, (CI 95%) 1.72 (1.18-2.51), p= 0.004 and 7.41 (5.4-10.1), p= <0.001). Comparatively, finding ≥2 IgGsc was the best predictor for a positive C3d.
*Conclusions: The ability of the IgG monoclonal abs to detect IgGsc depends on the MFI of the HLA-SAB; a high MFI improves the assessment of IgGsc. The HLA-DQ abs that were C3d positive had a higher probability of detection of IgGsc than any other combination. The classification of abs as one or more IgGsc increases the risk of these being C3d positive.
|IgG subclasses Detection (n=367)||Positive C3d assay (n=216)|
|HLA-Ab Class II, n (%)||636 (35.91)||116 (31.6)||161 (74.5)|
|HLA A, n (%)||291 (16.43)||69 (18.8)||23 (10.6)|
|HLA B, n (%)||566 (31.96)||145 (39.51)||22 (10.1)|
|HLA C, n (%)||278 (15.7)||37 (10.08)||10 (4.63)|
|HLA DP, n (%)||156 (8.81)||1 (0.27)||12 (5.56)|
|HLA DQ, n (%)||170 (9.6)||63 (17.17)||52 (24.07)|
|HLA DR, n (%)||310 (17.5)||52 (14.17)||97 (44.9)|
To cite this abstract in AMA style:Casillas-Abundis A, Arreola-Guerra JM, Alberu J, Solis-G MI, Llorente L, Granados J, Vilatoba M, Cruz-Martinez R, Morales-Buenrostro L, Contreras AG. Characterization of HLA Antibodies by C3d Assay and IgG Subclasses in Sensitized Kidney Transplant Patients [abstract]. Am J Transplant. 2019; 19 (suppl 3). https://atcmeetingabstracts.com/abstract/characterization-of-hla-antibodies-by-c3d-assay-and-igg-subclasses-in-sensitized-kidney-transplant-patients/. Accessed July 3, 2020.
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