Characteristics of CD103+CD8+ T cells in the spleen of Plasmodium yoelii NSM-infected mice.

Background: CD8+ T cells play a critical role in controlling Plasmodium infection. CD103, an integrin composed of αE and β7 subunits, is widely recognized as a cell surface marker for tissue-resident memory T (TRM) cells and tumor-infiltrating lymphocytes (TILs). Methods: In this study, a Plasmodium infection model was constructed by intraperitoneally injecting 106 infected red blood cells (iRBCs) into C57BL/6 mice. CD45+ cells in the spleen of naïve and infected mice were sorted and subjected to single-cell RNA sequencing (scRNA-seq). The content, activation, and function of CD103+CD8+ T cells were detected using flow cytometry. qPCR and dual-luciferase reporter assays were performed to find the key transcription factor. Results: Here, we identified a substantial subset of CD103+CD8+ T cells in the spleen of naïve mice, whose proportion and count declined rapidly following Plasmodium yoelii NSM infection. Compared to CD103-CD8+ T cells, in both naïve and infected mice, CD103+CD8+ T cells exhibited higher CD62L expression and lower levels of CD44, CD69, and TIGIT, and they rarely secreted IFN-γ or granzyme B upon PMA plus Ionomycin (PI) stimulation. Single-cell RNA sequencing revealed that differentially expressed genes (DEGs) were enriched in pathways related to "cytoplasmic translation" and "ribosome biosynthesis", suggesting that these cells are in a pre-activation preparatory state. Bioinformatics predictions and dual-luciferase reporter assays indicated that the transcription factor LEF1 may regulate Itgae transcription by binding to its promoter sequence. Conclusions: Collectively, our findings demonstrate that splenic CD103+CD8+ T cells express fewer activation and function-associated molecules, which may contribute to their limited role in the course of P. yoelii NSM infection in C57BL/6 mice, and implicates LEF1 in the regulation of CD103 expression.