During thymic negative selection, autoreactive thymocytes carrying T cell receptor (TCR) with overtly strong affinity to self-MHC/self-peptide are removed by Bim-dependent apoptosis, but how
Bim
is specifically regulated to link TCR activation and apoptosis induction is unclear. Here we identify a murine T cell-specific genomic enhancer
E
BAB
(
Bub1
-
Acoxl
-
Bim
)
, whose deletion leads to accumulation of thymocytes expressing high affinity TCRs. Consistently,
E
BAB
knockout mice have defective negative selection and fail to delete autoreactive thymocytes in various settings, with this defect accompanied by reduced
Bim
expression and apoptosis induction. By contrast,
E
BAB
is dispensable for maintaining peripheral T cell homeostasis via Bim-dependent pathways. Our data thus implicate
E
BAB
as an important, developmental stage-specific regulator of
Bim
expression and apoptosis induction to enforce thymic negative selection and suppress autoimmunity. Our study unravels a part of genomic enhancer codes that underlie complex and context-dependent gene regulation in TCR signaling.
This study reports a case of human immunodeficiency virus (HIV)-related natural killer/T-cell lymphoma with an unexpected clinical course. The lymphoma cells were positive for Epstein-Barr virus and the primary nodal lesions regressed after chemotherapy and combined antiretroviral therapy (c-ART); however, brain metastasis progressed along with a reduction in the CD8+ T-cell count. Chemotherapy was discontinued and the patient was treated with c-ART alone, resulting in regression of the brain lesions and recovery of the CD8+ T-cell count. This case highlights the importance of maintaining anti-tumor immunity in patients with HIV-related lymphoma.
Blood cells are thought to have emerged as phagocytes in the common ancestor of animals followed by the appearance of novel blood cell lineages such as thrombocytes, erythrocytes, and lymphocytes, during evolution. However, this speculation is not based on genetic evidence and it is still possible to argue that phagocytes in different species have different origins. It also remains to be clarified how the initial blood cells evolved; whether ancient animals have solely developed de novo programs for phagocytes or they have inherited a key program from ancestral unicellular organisms. Here, we traced the evolutionary history of blood cells, and cross-species comparison of gene expression profiles revealed that phagocytes in various animal species and Capsaspora (C.) owczarzaki, a unicellular organism, are transcriptionally similar to each other. We also found that both phagocytes and C. owczarzaki share a common phagocytic program, and that CEBPα is the sole transcription factor highly expressed in both phagocytes and C. owczarzaki. We further showed that the function of CEBPα to drive phagocyte program in nonphagocytic blood cells has been conserved in tunicate, sponge, and C. owczarzaki. We finally showed that, in murine hematopoiesis, repression of CEBPα to maintain nonphagocytic lineages is commonly achieved by polycomb complexes. These findings indicate that the initial blood cells emerged inheriting a unicellular organism program driven by CEBPα and that the program has also been seamlessly inherited in phagocytes of various animal species throughout evolution.
Although fatal pulmonary complications frequently occur during the course of acute leukemia, a minor proportion of the complications are due to leukemia itself. Infections, drug reactions and concomitant medical conditions are the major causes of respiratory distress in leukemic patients. We treated four patients with acute myeloid leukemia complicated by leukemic cell lysis pneumopathy (LCLP). All of the patients had leukemia of monocytoid origin and their respiratory function deteriorated soon after chemotherapy initiation. Although two of the patients required mechanical ventilation, all four improved after continued chemotherapy. Our experience indicates that, in cases of LCLP, chemotherapy should be continued with maximal respiratory support.
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