SIRPG and lymphopenia: The finding that SIRPG promotes T cell proliferation aligns with prior studies showing that SIRPG engagement with LSB2.20 enhances proliferation of anti-CD3 stimulated T cells (5), and is consistent with the T lymphopenia phenotype predicted for SIRPG by ARCHS4 (Massive Mining of Publicly Available RNA-seq Data from Human and Mouse) (34).