Understanding immunological response to desensitisation strategies in highly sensitised potential kidney transplant patients

Sensitisation to human leukocyte antigen (HLA) represents a significant barrier to kidney transplantation. Antibody removal and immune modulation strategies, known as 'desensitisation', aim to reduce levels of circulating HLA antibodies and increase transplant opportunities for highly sensitised patients (HSPs). However, the effects of desensitisation are generally transient and maintaining low or absent HLA antibody levels remains a substantial challenge. Furthermore, several studies report variation in patient response, with a proportion of desensitised patients able to replenish or maintain levels of circulating HLA specific antibodies despite receiving treatment to remove antibodies, antibody-producing plasma cells and their precursor B-cells. Various factors that influence the response to desensitisation have been proposed. However, the immune system is central, with differences in cytokine and leukocyte repertoire (i.e. the persistence of HLA antibody producing long-lived plasma cells (LLPCs) residing in the bone marrow) critical to desensitisation. Various cytokines are involved in commitment of B-cells to the LLPC fate, including interleukin (IL)-6, IL-21, B-cell activation factor (BAFF), a proliferation-inducing ligand (APRIL) and C-X-C motif chemokine 12 (CXCL12). Several studies have investigated variation in patient response to desensitisation with various immunological factors proposed as predictive biomarkers. However, this review reveals a need for larger studies to validate existing findings and a need for better understanding of the complex effects of desensitisation on immune profiles.