BTLA and systemic lupus erythematosus: However, even if aTregs from lupus patients still express lower levels of BTLA than other lupus CD4+ T cells (MFI 3188 ± 357 vs 9358 ± 559 in total CD4+ T cells, p<0.0001), we noticed a significant increase of BTLA expression on lupus aTregs compared to HC aTregs (MFI 2064 ± 228 vs 3188 ± 357, p<0.05; Figures 2C, D) as well as an enhancement of the frequency of BTLA-expressing aTregs in lupus patients [median of 79% (range 15-100), Figure 2E].