Biology subjects

Shallberg, L. A.

Publications and source records attributed to Shallberg, L. A..

4 recordsLinked to original sources

bioRxiv2024

NF-κB Signaling is Required for X-Chromosome Inactivation Maintenance Following T cell Activation

X Chromosome Inactivation (XCI) is a female-specific process which balances X-linked gene dosage between sexes. Unstimulated T cells lack cytological enrichment of Xist RNA and heterochromatic modifications on the inactive X chromosome (Xi), and these modifications become enriched at the Xi after cell stimulation. Here, we examined allele-specific gene expression and the epigenomic profiles of the Xi following T cell stimulation. We found that the Xi in unstimulated T cells is largely dosage compensated and is enriched with the repressive H3K27me3 modification, but not the H2AK119-ubiquitin (Ub) mark, even at promoters of XCI escape genes. Upon CD3/CD28-mediated T cell stimulation, the Xi accumulates H2AK119-Ub and H3K27me3 across the Xi. Next, we examined the T cell signaling pathways responsible for Xist RNA localization to the Xi and found that T cell receptor (TCR) engagement, specifically NF-{kappa}B signaling downstream of TCR, is required. Disruption of NF-{kappa}B signaling, using inhibitors or genetic deletions, in mice and patients with immunodeficiencies prevents Xist/XIST RNA accumulation at the Xi and alters expression of some X-linked genes. Our findings reveal a novel connection between NF-{kappa}B signaling pathways which impact XCI maintenance in female T cells.

immunology↗

bioRxiv2023

Dendritic cell-mediated responses to secreted Cryptosporidium effectors are required for parasite-specific CD8+ T cell responses

Cryptosporidium causes debilitating diarrheal disease in patients with primary and acquired defects in T cell function. However, it has been a challenge to understand how this infection generates T cell responses and how they mediate parasite control. Here, Cryptosporidium was engineered to express a parasite effector protein (MEDLE-2) that contains the MHC-I restricted SIINFEKL epitope which is recognized by TCR transgenic OT-I CD8+ T cells. These modified parasites induced expansion of endogenous SIINFEKL-specific and OT-I CD8+ T cells that were a source of IFN-{gamma} that could restrict growth of Cryptosporidium. This T cell response was dependent on the translocation of the effector and similar results were observed with another secreted parasite effector (ROP1). Although infection and these translocated effector proteins are restricted to intestinal epithelial cells (IEC), type I dendritic cells (cDC1) were required to generate CD8+ T cell responses to these model antigens. These data sets highlight Cryptosporidium effectors as targets of the immune system and suggest that crosstalk between enterocytes and cDC1s is crucial for CD8+ T cell responses to Cryptosporidium.

immunology↗

bioRxiv2022

Impact of secondary TCR engagement on the heterogeneity of pathogen-specific CD8+ T cell response during acute and chronic toxoplasmosis

Initial TCR engagement of CD8+ T cells results in T cell expansion, and these early events influence the generation of diverse effector and memory populations. During infection, some activated T cells re-encounter cognate antigen, but how these events influence local effector responses or formation of memory populations is unclear. To address this issue, OT-I T cells which express the Nur77-GFP reporter of TCR activation were paired with T. gondii that express OVA to assess the impact of TCR activation on CD8+ T cell responses. During acute infection, TCR stimulation in affected tissues correlated with parasite burden and was associated with markers of effector cells while Nur77-GFP- OT-I showed signs of effector memory potential. However, adoptive transfer of Nur77-GFP negative or positive OT-I from infected mice into naive recipients resulted in formation of similar memory populations. During the chronic stage of infection in the CNS, TCR activation was associated with large scale transcriptional changes and the acquisition of an effector T cell phenotype as well as the generation of a population of CD103+ CD69+ Trm like cells. However, while inhibition of parasite replication resulted in reduced effector responses it did not alter the Trm population. These data sets highlight the contribution of recent TCR activation on the phenotypic heterogeneity of the CD8+ T cell response but suggest that this process has a limited impact on memory populations at acute and chronic stages of infection. Author SummaryCD8+ T cells are important to control many acute and chronic infections, however the role that recent T cell receptor stimulation plays in the formation of ongoing T cell responses is unclear. Here, we utilize a genetic reporter of TCR stimulation and high parameter flow cytometry to characterize TCR-driven phenotypes of pathogen specific T cell responses to the parasite Toxoplasma gondii during acute and chronic infection in the periphery and central nervous system. This work demonstrates the importance of recent TCR stimulation in driving local effector CD8+ T cell responses in peripheral tissues during infection, as well as the plasticity of the formation of memory T cells. Additionally, we utilize static and live imaging to investigate how Toxoplasma gondii life cycle impacts the ability to present antigen to CD8+ T cells. These studies aid in our understanding of how effector and memory CD8+ T cell responses are generated and maintained during an infection.

immunology↗

bioRxiv2020

cDC1 Coordinate Innate and Adaptive Responses in the Omentum required for T cell Priming and Memory

The omentum in the peritoneal cavity contains fat associated lymphoid clusters (FALCs) whose role in the response to microbial challenge are poorly understood. After intraperitoneal immunization with Toxoplasma gondii, type I dendritic cells (cDC1) were critical to induce innate sources of IFN-{gamma} required to recruit monocytes to the FALCs. The migration of infected peritoneal macrophages into T and B cell rich areas of the FALCs allowed the TCR-induced activation of parasite-specific T cells. Unexpectedly, cDC1 were not required for T cell priming but rather supported the expansion of parasite-specific CD8+ T cells. An agent-based mathematical model predicted that the lack of cDC1 would impact the early proliferative burst, and we confirmed that cDC1 were required for optimal T cell expression of nutrient uptake receptors and cell survival. These studies highlight that cDC1 in the FALCs have distinct roles in the co-ordination of the innate and adaptive responses to microbial challenge.

immunology↗