We have produced transgenic mice expressing hen egg-white lysozyme (HEL) under the control of a ubiquitous promoter, so that in transgenic animals, HEL is presumably present in the serum and thymus throughout the period of establishment of the T-cell repertoire. We show that HEL transgenic H-2d mice with HEL blood levels >10 ng/ml are tolerant to HEL as well as to the immunodominant peptide 108-116. Thus, their T lymphocytes do not proliferate in response to the immunodominant peptide 108-116 after in vivo immunization with HEL or peptide 108-116. In contrast, in transgenic mice tolerant to HEL, the state of tolerance to subdominant peptides 1-18 and 74-96 appears variable and highly dependent on HEL blood levels. Complete unresponsiveness is seen when HEL serum levels are high, and this unresponsiveness is reached at a lower HEL concentration for peptide 1-18 than for peptide 74-96. Thus, a hierarchy exists among the three peptides (108-116 >> 1-18 > 74-96) for induction of a response to HEL and for HEL tolerance induction in T cells specific for these peptides. Persistence in the periphery of autoreactive T cells recogiing subdominant peptides of self-proteins, as shown in this transgenic model, indicates that self-tolerance is limited to a subset of dominant self-peptides and suggests a role for T lymphocytes specific for subdominant determinants in autoimmunity.

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a life-threatening, immunologically mediated, and usually drug-induced disease with a high burden to individuals, their families, and society with an annual incidence of 1 to 5 per 1,000,000. To effect significant reduction in short- and long-term morbidity and mortality, and advance clinical care and research, coordination of multiple medical, surgical, behavioral, and basic scientific disciplines is required. On March 2, 2017, an investigator-driven meeting was held immediately before the American Academy of Dermatology Annual meeting for the central purpose of assembling, for the first time in the United States, clinicians and scientists from multiple disciplines involved in SJS/TEN clinical care and basic science research. As a product of this meeting, this article summarizes the current state of knowledge and expert opinion related to SJS/TEN covering a broad spectrum of topics including epidemiology and pharmacogenomic networks; clinical management and complications; special populations such as pediatrics, the elderly, and pregnant women; regulatory issues and the electronic health record; new agents that cause SJS/TEN; pharmacogenomics and immunopathogenesis; and the patient perspective. Goals include the maintenance of a durable and productive multidisciplinary network that will significantly further scientific progress and translation into prevention, early diagnosis, and management of SJS/TEN.

SummaryWe have previously produced a transgenic mouse line for hen egg lysozyme (HEL), an experimental model for analyzing tolerance to self-antigens at the peptide level. We have now characterized transgenic mice with HEL blood levels below 2 ng/ml, where significant T cell proliferative responses to HEL and its immunodominant peptide were observed. This HEL-low transgenic model was chosen because it mimics physiological conditions in which autoreactive T lymphocytes, recognizing self-components expressed at very low levels, persist without inducing a break in tolerance. Furthermore, in H-2 d mice, HEL-specific T lymphocytes are triggered by a single immunodominant region, allowing us to compare the HEL-specific T cell VB repertoires of transgenic and nontransgenic animals against a single peptide presented as self or foreign, respectively. We found that a V/38.2-D/31-J/31.5 rearrangement is found in response to HEL in all nontransgenic mice, whereas this V/3-restricted response is absent in HEL-low transgenic animals. At the nucleotide level, this rearrangement results from the trimming of the genomic segments during VDJ or DJjoining, without N additions, suggesting that the dominant rearrangement is selected early during fetal or neonatal life, before the expression of terminal deoxynucleotidyl transferase. In HEL-low transgenic mice, no dominant rearrangements are found as alternatives to the one observed in normal mice. Instead, each transgenic animal uses a different set of V~-J/3 combinations in its response to the immunodominant HEL peptide. In nontransgenic mice, besides the dominant VB8.2-D/31-J~l.5 combination, minor VB repertoires were found which differed in each animal and were distinct from the rearrangements used by individual transgenic mice. These findings suggest that the T cell response to an immunodominant peptide involves a "public" V/5 repertoire found in all animals and a "private" one which is specific to each individual.

A central paradigm of T cell development is that CD4+8+ (DP) thymocytes differentiate into CD4+ or CD8+ T cells in response to intrathymic signals that extinguish transcription of the inappropriate coreceptor molecule. Contrary to this prevailing paradigm, we now demonstrate that signaled DP thymocytes initially terminate CD8 transcription even when differentiating into CD8+ T cells. Remarkably, thymocytes that have selectively terminated CD8 transcription can be signaled by IL-7 to differentiate into CD8+ T cells by silencing CD4 transcription and reinitiating CD8 transcription, events we refer to as "coreceptor reversal." These observations significantly alter our understanding of CD8+ T cell differentiation and lead to a new perspective ("kinetic signaling") on CD4/CD8 lineage determination in the thymus. These observations also suggest a novel mechanism by which bipotential cells throughout development can determine their appropriate cell fate.

Differentiation of immature double positive (DP) CD4+ CD8+ thymocytes into single positive (SP) CD4+ and CD8+ T cells is referred to as positive selection and requires physical contact with thymic cortical epithelium. We now have identified "coinducer" molecules on DP thymocytes that, together with TCR, signal DP thymocytes to differentiate into SP T cells in vitro in the absence of thymic epithelium. A remarkable number of different molecules on DP thymocytes possessed "coinducing" activity, including CD2, CD5, CD24, CD28, CD49d, CD81, and TSA-1. Interestingly, in vitro differentiation occurred in the absence of lineage-specific signals, yet resulted in the selective generation of CD4+CD8- T cells. Thus, the present study has identified surface molecules that can signal DP thymocytes to differentiate into SP T cells in the absence of thymic epithelium and has characterized a default pathway for CD4+ T cell differentiation.

Increased Type I IFNs or IFN-I have been associated with human systemic lupus erythematosus. Interestingly augmenting or negating IFN-I activity in murine lupus not only modulates systemic autoimmunity, but also impacts lupus nephritis, suggesting that IFN-I may be acting at the level of the end-organ. We find resident renal cells to be a dominant source of IFN-I in an experimental model of autoantibody-induced nephritis. In this model, augmenting IFN-I amplified antibody-triggered nephritis, whereas ablating IFN-I activity ameliorated disease. One mechanism through which increased IFN-I drives immune-mediated nephritis might be operative through increased recruitment of inflammatory monocytes and neutrophils, though this hypothesis needs further validation. Collectively, these studies indicate that an important contribution of IFN-I toward the disease pathology seen in systemic autoimmunity may be exercised at the level of the end-organ.

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are potentially lifethreatening, immune-mediated adverse reactions characterized by widespread erythema, epidermal necrosis, and detachment of skin and mucosa. Efforts to grow and develop functional international collaborations and a multidisciplinary interactive network focusing on SJS/TEN as an uncommon but high burden disease will be necessary to improve efforts in prevention, early diagnosis and improved acute and long-term management. SJS/TEN 2019: From Science to Translation was a 1.5-day scientific program held April 26-27, 2019, in Vancouver, Canada. The meeting successfully engaged clinicians, researchers, and patients and conducted many productive discussions on research and patient care needs.

A coordinated effort combining bioinformatic tools with high-throughput cell-based screening assays was implemented to identify novel factors involved in T-cell biology. We generated a unique library of cDNAs encoding predicted secreted and transmembrane domain-containing proteins generated by analyzing the Human Genome Sciences cDNA database with a combination of two algorithms that predict signal peptides. Supernatants from mammalian cells transiently transfected with this library were incubated with primary T cells and T-cell lines in several high-throughput assays. Here we describe the discovery of a T cell factor, TIP (T cell immunomodulatory protein), which does not show any homology to proteins with known function. Treatment of primary human and murine T cells with TIP in vitro resulted in the secretion of IFN-gamma, TNF-alpha, and IL-10, whereas in vivo TIP had a protective effect in a mouse acute graft-versus-host disease (GVHD) model. Therefore, combining functional genomics with high-throughput cell-based screening is a valuable and efficient approach to identifying immunomodulatory activities for novel proteins.