BATF transgenic mice: Investigating the role of AP-1 in the development and function of natural killer T lymphocytes
BATF belongs to the AP-1 family of bZIP transcription factors and dimerizes with Jun proteins to negatively regulate the transcription of AP-1 target genes. BATF is expressed in hematopoietic cells and previous studies suggested a role for BATF in modulating the AP-1 activity of thymic and peripheral T cells. To examine this further, transgenic mice were generated in which HA epitope tagged BATF is expressed using the constitutive, T cell-specific p56lck or hCD2 promoters. While BATF transgenic mice exhibit a normal profile of the major T cell subsets, cytometric, molecular and functional analysis has revealed that BATF transgenic mice are specifically deficient in glycolipid reactive, Natural Killer T (NKT) lymphocytes. Analysis of the residual NKT cells in BATF transgenic mice with CD1d multimer technology has revealed that HA-BATF targets all classes of NKT cell regardless of Vβ usage or CD4 expression. Developmental tracking experiments have demonstrated that HA-BATF impacts the expansion, maturation, and survival of positively selected, yet immature, NKT cells within the thymus. However, transgenic NKT cells that manage to complete maturation can form reduced, but stable, peripheral NKT cell populations that appear tolerant of HA-BATF and are maintained throughout the life of the mice. The phenotype of BATF transgenic mice suggested for the first time that AP-1 is present in NKT cells and plays an important role in early NKT cell development. Purification of thymic NKT cells and analysis of AP-1 transcripts has revealed the full complement of AP-1 factors. In addition, AP-1 DNA binding activity has been detected in NKT cell hybridomas and primary cultures within six hours of treatment with plate bound CD1d and α-galactosylceramide. Analysis of antigen presentation has revealed that antigen presenting cells present glycolipid ligand and induce AP-1 activity in the same six-hour time frame. Lastly, transcription of the AP-1 target gene IL-4 in response to α-GalCer is a rapid event occurring within 3 hours of activation and appears sensitive to ERK inhibition. When coupled with the phenotype of BATF transgenic mice, the data presented begins to characterize AP-1 as an early response factor in NKT cells and a critical mediator of NKT cell survival and development in the thymus.
Taparowsky, Purdue University.
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