Rise of a CD27- IgD- CD11c+ B cells population in kidney recipients achieving long-term graft stability under immunosuppression.

The use of immunosuppressive treatment is required to prevent rejection events, even a long time after kidney transplantation despite rare recipients achieving long-term graft stability without the need for immunosuppressive treatment, called operationally tolerant patients (TOLs). We comprehensively investigate the immune system of long-term IS recipients (LTTs) and TOLs to highlight their shared and unique immune features. Blood immune cell phenotyping was performed by spectral cytometry. Samples from 34 individuals were analyzed, including 6 LTTs, 8 TOLs, 10 stable patients at 1 year posttransplantation (STAs), and 10 healthy volunteers. B cells differed between LTTs and TOLs with a decreased total B-cell frequency and the acquisition of a memory phenotype in LTTs whereas a naive phenotype is maintained in TOLs. The frequencies of IgD^-CD27^- B cells and CD11c⁺ memory B cells are increased in LTTs, with an exhausted phenotype, evoked by a significant decrease in CD25 expression. These CD11c⁺ B cells display an exhausted phenotype similar to those found in several chronic immune diseases in which they have been shown to participate in their pathophysiology, suggesting active chronic inflammation in LTTs. Altogether, these data indicate that precautions should be taken to minimize IS use.