Interactions of the TCR with self peptide–MHC are crucial to T cell development. Allen and colleagues show that the strength of such interactions also determines the intrinsic T cell functionality and responses to pathogens. Interactions of T cell antigen receptors (TCRs) with complexes of self peptide and major histocompatibility complex (MHC) are crucial to T cell development, but their role in peripheral T cell responses remains unclear. Specific and nonspecific stimulation of LLO56 and LLO118 T cells, which transgenically express a TCR specific for the same Listeria monocytogenes epitope, elicited distinct interleukin 2 (IL-2) and phosphorylated kinase Erk responses, the strength of which was set in the thymus and maintained in the periphery in proportion to the avidity of the binding of the TCR to the self peptide–MHC complex. Deprivation of self peptide–MHC substantially compromised the population expansion of LLO56 T cells in response to L. monocytogenes in vivo. Despite their very different self-reactivity, LLO56 T cells and LLO118 T cells bound cognate peptide–MHC with an identical affinity, which challenges associations made between these parameters. Our findings highlight a crucial role for selecting ligands encountered during thymic 'education' in determining the intrinsic functionality of CD4+ T cells.

Th cell subsets have unique calcium (Ca²⁺) signals when activated with identical stimuli. The regulation of these Ca²⁺ signals and their correlation to the biological function of each T cell subset remains unclear. Trpm4 is a Ca²⁺-activated cation channel that we found is expressed at higher levels in Th2 cells compared with Th1 cells. Inhibition of Trpm4 expression increased Ca²⁺ influx and oscillatory levels in Th2 cells and decreased influx and oscillations in Th1 cells. This inhibition of Trpm4 expression also significantly altered T cell cytokine production and motility. Our experiments revealed that decreasing Trpm4 levels divergently regulates nuclear localization of NFATc1. Consistent with this, gene profiling did not show Trpm4-dependent transcriptional regulation, and T-bet and GATA-3 levels remain identical. Thus, Trpm4 is expressed at different levels in Th cells and plays a distinctive role in T cell function by differentially regulating Ca²⁺ signaling and NFATc1 localization.

The T cell receptor (TCR) αβ heterodimer determines the peptide and MHC specificity of a T cell. It has been proposed thatin vivoselection processes maintain low TCR affinities because T cells with higher-affinity TCRs would (i) have reduced functional capacity or (ii) cross-react with self-peptides resulting in clonal deletion. We used the class II-restricted T cell clone 3.L2, specific for murine hemoglobin (Hb/I-E^k), to explore these possibilities by engineering higher-affinity TCR mutants. A 3.L2 single-chain TCR (Vβ-linker-Vα) was mutagenized and selected for thermal stability and surface expression in a yeast display system. Stabilized mutants were used to generate a library with CDR3 mutations that were selected with Hb/I-E^kto isolate a panel of affinity mutants withK_Dvalues as low as 25 nM. Kinetic analysis of soluble single-chain TCRs showed that increased affinities were the result of both faster on-rates and slower off-rates. T cells transfected with the mutant TCRs and wild-type TCR responded to similar concentrations of peptide, indicating that the increased affinity was not detrimental to T cell activation. T cell transfectants maintained exquisite hemoglobin peptide specificity, but an altered peptide ligand that acted as an antagonist for the wild-type TCR was converted to a strong agonist with higher-affinity TCRs. These results show that T cells with high-affinity class II reactive TCRs are functional, but there is an affinity threshold above which an increase in affinity does not result in significant enhancement of T cell activation.

Since the completion of the Human Genome Project in 2003, genomic sequencing has become a prominent tool used by diverse disciplines in modern science. In the past 20 years, the cost of genomic sequencing has decreased exponentially, making it affordable and accessible. Bioinformatic and biological studies have produced significant scientific breakthroughs using the wealth of genomic information now available. Alongside the scientific benefit of genomics, companies offer direct-to-consumer genetic testing which provide health, trait, and ancestry information to the public. A key area that must be addressed is education about what conclusions can be made from this genomic information and integrating genomic education with foundational genetic principles already taught in academic settings. The promise of personal genomics providing disease treatment is exciting, but many challenges remain to validate genomic predictions and diagnostic correlations. Ethical and societal concerns must also be addressed regarding how personal genomic information is used. This genomics revolution provides a powerful opportunity to educate students, clinicians, and the public on scientific and ethical issues in a personal way to increase learning. In this review, we discuss the influence of personal genomics in society and focus on the importance and benefits of genomics education in the classroom, clinics, and the public and explore the potential consequences of personal genomic education.

Helper T cells are critical for protective immunity, CD8 ⁺ T-cell memory, and CD4 ⁺ recall responses, but whether the same or distinct CD4 ⁺ T cells are involved in these responses has not been established. Here we describe two CD4 ⁺ T cells, LLO118 and LLO56, specific for an immunodominant Listeria monocytogenes epitope, with dramatically different responses to primary and secondary infection. Comparing in vivo responses, LLO118 T cells proliferate more strongly to primary infection, whereas surprisingly, LLO56 has a superior CD4 ⁺ recall response to secondary infection. LLO118 T cells provide more robust help for CD8 ⁺ T-cell responses to secondary infection than LLO56. We found no detectable differences in antigen sensitivity, but naive LLO118 T cells have much lower levels of CD5 and their T-cell receptor levels are dramatically down-regulated after their strong primary response. Thus, distinct CD4 ⁺ helper T cells are specialized to help either in primary or secondary responses to infection.