Back to the future: the uncharted role of T cells in chronic and unexplained microvascular inflammation.

The 2022 Banff classification for kidney allograft pathology introduced the category "microvascular inflammation DSA-negative and C4d-negative" for cases without evidence of a humoral cause. Many questions remain about the etiology, prognosis, and treatment of this phenotype. Cristoferi et al. performed a molecular comparison of chronic active antibody-mediated rejection and its seronegative counterpart and suggest a central role for T cells in chronic donor-specific antibody-negative, C4d-negative microvascular inflammation. These results further question how we should classify rejection.