Body: The case presents a patient who underwent heart transplantation (txp) with 0% CPRA and no donor-specific antibodies (DSA). High-level pre-txp antibodies against the angiotensin II type 1 receptor (AT1R) were identified when tested 3 months post-transplant. Plasma exchange sessions were immediately initiated. Despite these interventions, the patient's clinical course was complicated by a diagnosis of antibody-mediated rejection, graded as ISHLT (2013) p AMR (H1), 22 months after txp. The AT1R antibody levels were significantly high, exceeding the limit of detection pre- and post-txp, regardless of plasma exchange treatment and losartan medication. However, over the following 6 months with a monthly Tocilizumab (IL-6 blockage, 8mg/kg) protocol, the AT1R antibody level began to decline as evidenced by its level at 1:500 serum dilution (from >40 to 13 U/ml), while still being saturated (>40 U.ml) at 1:100 serum dilution. After 5 sessions of Tocilizumab, reduced anti-AT1R levels were finally confirmed even at 1:100. In contrast, the levels of autoantibodies remained constant or fluctuated for some, but no major decrease was observed. The patient was discharged with improved graft function.
Conclusion: The case demonstrated that AT1R antibodies, unlike other non-HLA antibodies (39 specificities tested in the panel), were significantly reduced during tocilizumab administration but not with TPE +/- IVIG. While non-HLA antibodies are critical in measuring desensitization efficacy in the absence of DSA, the impact of tocilizumab could be best assessed by changes in anti-AT1R levels at 1:500 serum dilution before becoming detectable at 1:100, indicating its potential effect of tocilizumab on the AT1T antibody level.
