Tissue-distinct Features of Follicular Cytotoxic CD8+ T Cells in Trypanosoma cruzi infection.

T follicular cytotoxic (Tfc) cells are a specialized subset of CD8+ T lymphocytes that combine helper and cytotoxic functions. While their phenotypic and functional properties have been described in several infectious and inflammatory settings, little is known whether Tfc cells exhibit distinct characteristics across secondary lymphoid organs. Using acute Trypanosoma cruzi infection as a model of systemic immune activation, we performed a comparative phenotypic, transcriptomic, metabolic, and functional characterization of Tfc cells arising in the spleen and inguinal lymph nodes. Tfc cells emerged transiently in both organs with similar kinetics and antigen specificity yet segregated primarily according to tissue of analysis at the transcriptional level. Splenic Tfc cells exhibited enhanced glycolytic and mTORC1-associated signatures, increased mitochondrial mass, and stronger cytotoxic and B cell helper functions, promoting immunoglobulin production and plasmablast death. In contrast, Tfc cells from lymph node preferentially displayed memory-associated features, including higher CD127 and CD122 expression, increased IL-2 production, and preferential persistence during chronic infection. Together, these findings demonstrate that Tfc cells are not a homogeneous population but can adopt organ-associated transcriptional, metabolic, and functional states during T. cruzi infection.