In vivo or in vitro conversion of peripheral CD4⁺ T cells to CD4⁻ T cells via auto- or alloantigen-triggered or homeostatic proliferation. (A) Flow cytometry of CD4⁻ cells converted from C57BL/6 (CD45.1) CD4⁺ T cells via mitomycin C–treated DBA/2 APC stimulation in vitro. (B) Flow cytometry of CD4⁻ cells converted from C57BL/6 (CD45.1) CD4⁺ T cells via syngeneic mDC stimulation in vitro. (C) CFSE-labeled C57BL/6 (CD45.1) CD4⁺ T cells were transferred to B6D2F1 mice by intravenous injection. Flow cytometry of CD4⁻ cells converted from C57BL/6 (CD45.1) CD4⁺ T cells harvested from spleens and lymph nodes of B6D2F1 mice on day 3. (D) CFSE-labeled C57BL/6 (CD45.1) CD4⁺ T cells were transferred to syngeneic Rag KO mice by intravenous injection. Flow cytometry of CD4⁻ cells converted from C57BL/6 (CD45.1) CD4⁺ T cells harvested from spleens and lymph nodes of syngeneic Rag KO mice on day 7. (E) Flow cytometry of CD4⁻ cells converted from C57BL/6 TEa transgenic CD4⁺ T cells via CB6F1 mDC stimulation in vitro. Numbers refer to the percentages of gated CD4⁻ cells.