Hobit and Blimp-1 instruct the differentiation of iNKT cells into resident-phenotype lymphocytes after lineage commitment.

iNKT cells are CD1d-restricted T cells that play a pro-inflammatory or regulatory role in infectious and autoimmune diseases. Thymic precursors of iNKT cells eventually develop into distinct iNKT1, iNKT2, and iNKT17 lineages in the periphery. It remains unclear whether iNKT cells retain developmental potential after lineage commitment. iNKT cells acquire a similar phenotype as tissue-resident memory T cells, suggesting that they also differentiate along a trajectory that enables them to persist in peripheral tissues. Here, we addressed whether lineage commitment and memory differentiation are parallel or sequential developmental programs of iNKT cells. We defined three subsets of peripheral iNKT cells using CD62L and CD69 expression that separate central, effector, and resident memory phenotype cells. The majority of iNKT1 cells displayed a resident phenotype in contrast to iNKT2 and iNKT17 cells. The transcription factor Hobit, which is upregulated in iNKT cells, plays an essential role in their development together with its homolog Blimp-1. Hobit and Blimp-1 instructed the differentiation of central memory iNKT cells into resident memory iNKT cells, but did not impact commitment into iNKT1, iNKT2, or iNKT17 lineages. Thus, we conclude that memory differentiation and the establishment of residency occur after lineage commitment through a Hobit and Blimp-1-driven transcriptional program.

Adequate synapse formation between leukemic B cells and effector T cells following stimulation with artificial TCR ligands.

Artificial T cell receptor (TCR) ligands can be used to direct virus-specific cytotoxic T lymphocytes (CTL) towards tumor cells. Because of their size, these constructs may differ from cognate peptides in their ability to induce T cell activation. We here analysed signalling outcomes upon synapse formation between human cytomegalovirus (CMV)-specific CTL and chronic lymphocytic leukemia (CLL) cells through targeted complexes (TC) containing anti-CD20 single-chain variable fragment and biotinylated major histocompatibility complex class I molecules presenting peptides from CMVpp65. TC coated CLL cells were effectively lysed by CMVpp65-specific CTL but induced less interferon gamma (IFN-gamma) production than peptide loaded targets. Confocal microscopy revealed that TC induced a redistribution of TCR/CD3 but not CD2 towards the immunological synapse. Furthermore, morphological examination of immunological synapses showed smaller and 'patchy' interactions between TC coated B cells and CTL as compared with peptide coated targets. Finally, pre-incubation of CTL with CD2 antibodies led to an Fc-dependent redistribution of CD2 into TC-induced synapses and restored IFN-gamma production by CMV-specific CTL. Thus, redistribution of CD2 towards the immunological synapse appears to be essential for full T cell activation. However, CD2 triggering is not required for efficient lysis of tumor cells, demonstrating that CTL require only minimal stimulation to release their cytotoxic content.