TCL1B (TCL1 family AKT coactivator B) is a 14-kDa protein that functions as a critical coactivator of the AKT kinase, a central regulator of cell survival and proliferation signaling. TCL1B enhances AKT phosphorylation and activation through direct physical interaction with AKT's pleckstrin homology domain, facilitating AKT oligomerization and promoting its translocation to the nucleus 1. This protein is predominantly expressed in immature T cells and virgin B cells, with expression declining during differentiation 2. TCL1B shares 60% sequence similarity with TCL1 and comparable expression patterns, suggesting redundant or complementary functions 3. Pathologically, TCL1B is activated as an oncogene in T-cell leukemias through chr14 translocations and inversions at 14q32.1 that juxtapose it to T-cell receptor regulatory elements 24. Activation of TCL1B in mature T cells promotes oncogenic transformation by enhancing PI3K-dependent AKT signaling, which promotes cell survival rather than proliferation alone 2. Recently, TCL1B variants have been identified through genome-wide association studies as having ancestry-specific effects on clonal hematopoiesis development, indicating its relevance to age-related hematologic conditions 5.