Page 202 - 2019_02-Haematologica-web

M. Rijkers et al.
Results
HLA antibody WIM8E5 induces complement C3b and C4b deposition on platelets
Human HLA mAbs recognizing different epitopes encoded by different HLA class I subtypes (Online Supplementary Table S1) were incubated with platelets from donors with an HLA type matching the specificity of the mAbs, in the presence of normal human serum.
Complement deposition of C3b on platelet surfaces increased upon incubation with increasing concentrations of HLA mAb WIM8E5 (specific for an epitope present on all HLA-A antigens except for HLA-A3 and-A32 and with reduced binding to HLA-A2) (Figure 1A). Statistically sig- nificant increased C3b deposition was observed with 20 mg/ml WIM8E5 (Figure 1B). Also, C4b deposition on platelet surfaces was significantly increased when platelets were incubated with WIM8E5 (Figure 1C-D). A
A
B
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D
Figure 2. Combinations of HLA mAbs induce enhanced complement activation. (A) Four different HLA mAbs were incubated with HLA matched platelets both sep- arately and in combination (20 mg/ml per antibody) and C3b deposition was measured. (B-C) Examples of C3b deposition induced by HLA mAbs separately and in combination (20 mg/ml per HLA mAb). (D) C3b deposition on platelets of 2 donors by a combination of anti-HLA-A2 antibodies SN607D8 and SN230G6 at 0.0125 - 10 mg/ml. HLA donor 1: A2 A31 B60 HLA donor 2: A2 A68 B51 B57.
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haematologica | 2019; 104(2)