Spontaneous and Allo-Antibody (Ab)-Stimulated IFNγ Production in NK Cells as Detected By Cytokine Flow Cytometry (Allo-CFC) Decreased in HLA-Sensitized Kidney Transplant Patients (HS Tx Pts) Desensitized With Tocilizumab (TCZ, Anti-IL-6R)+Intravenous Immunoglobulin (IVIG).

Abstract

Background: TCZ has anti-B cell and anti-inflammatory properties. Analysis of allo-Ab and Ab producing cell modification by desensitization (DES) with TCZ+IVIG in HS pts is underway. We have shown elevated IFNγ+ NK cellsvia ADCC-like mechanism after exposure to allo-PBMCsas analyzed by Allo-CFC. This suggests an important role of NK cells in antibody-mediated rejection. The effect of TCZ on ADCC is not known. Here, we examine the effects of “TCZ+IVIG” DES on IFNg production by NK cells stimulated by anti-HLA ADCC in HS pts with the DES. Methods: Blood from 6 pts desensitized with TCZ+IVIG (IVIG 2g/kg, x2, 1M apart; TCZ [8mg/kg], up to 7x, monthly) were submitted for NK cell subset analysis and Allo-CFC. In the Allo-CFC, IFNγ+ cell% in CD56+ NK cells were enumerated. Those obtained from 17 pts desensitized with rituximab+IVIG were used as control. PRA class I & class II (PRAI, PRAII) were performed by Luminex. Results: IFNγ+ NK cell% in the Allo-CFC significantly decreased by 4M post-TCZ in all 6 pts (100%, 3.8±5.1 vs. 5.6±6.1 pre-TCZ, p=0.03), and 3/4 pts (75%) with the available results at 0.5M post-TCZ already showed the reduction (3.9±3.3 vs. 5.9±2.6 pre-TCZ, p=0.19). Reduction of IFNγ+ cell% in NK cells without allo-PBMC stimulation (background) was also observed at 4M and 0.5M post-TCZ in all 6 and 4pts, respectively (1.4±0.8 vs. 3.0±1.0 pre-TCZ, p<0.02; 1.6±0.4 vs. 2.9±1.2, p=0.1). These trends were not observed in pts treated with “rituximab+IVIG” DES; Only 9/17 (53 vs. 75% in TCZ-DES, p<0.01) and 8/17 (47 vs. 100%, p<0.01) showed Allo-CFC and IFNγ background reduction at 0.5M post-rituximab, respectively. CD56+ (63±38/μl vs.49±35/μl pre-TCZ), CD16+ NK cell number (55±36/μl vs. 46±32 /μl), PRAI (86±26 vs. 88±23 %) & PRAII (93±7 vs. 91±9%), factors affecting the Allo-CFC (in vitro ADCC), did not significantly change by 4M post-TCZ. Conclusions: Spontaneous and allo-Ab-mediated IFNγ production in NK cells decreased after the “TCZ+IVIG” DES. This observation suggests that TCZ could suppress NK cell IFNg production in HS kidney Tx pts, which may regulate ADCC-mediated allograft injury post-Tx. DISCLOSURES:Jordan, S.: Grant/Research Support, CSL-Behring, Genentech Roche.