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Introduction: Insulin-like growth factor 1 receptor (IGF1R) mutations lead to systemic disturbances in growth and glucose homeostasis due to widespread IGF1R expression throughout the body. IGF1R is expressed by innate and adaptive immune cells, facilitating their development and exerting immunomodulatory roles in the periphery. Case Presentation: We report on a family presenting with a novel heterozygous IGF1R mutation with characterization of the mutation, IGF1R expression, and immune phenotyping. Twin probands presented clinically with short stature and hypoglycemia. Variable phenotypic expression was seen in 2 other family members carrying the IGF1R mutation. The probands were treated with exogenous growth hormone therapy and dietary cornstarch, improving linear growth and reducing hypoglycemic events. IGF1R c.641-2A>G caused abnormal mRNA splicing and premature protein termination. Flow cytometric immunophenotyping demonstrated lower IGF1R on peripheral blood mononuclear cells from IGF1R c.641-2A>G subjects. This alteration was associated with reduced levels of T-helper 17 cells and a higher percentage of T-helper 1 cells compared to controls, suggesting decreased IGF1R expression may affect CD4+ Th-cell lineage commitment. Discussion: Collectively, these data suggest a novel loss-of-function mutation (c.641-2A>G) leads to aberrant mRNA splicing and IGF1R expression resulting in hypoglycemia, growth restriction, and altered immune phenotypes. [ABSTRACT FROM AUTHOR]

Infancy and childhood are critical life stages for generating immune memory to protect against pathogens; however, the timing, location, and pathways for memory development in humans remain elusive. Here, we investigated T cells in mucosal sites, lymphoid tissues, and blood from 96 pediatric donors aged 0–10 years using phenotypic, functional, and transcriptomic profiling. Our results revealed that memory T cells preferentially localized in the intestines and lungs during infancy and accumulated more rapidly in mucosal sites compared with blood and lymphoid organs, consistent with site-specific antigen exposure. Early life mucosal memory T cells exhibit distinct functional capacities and stem-like transcriptional profiles. In later childhood, they progressively adopt proinflammatory functions and tissue-resident signatures, coincident with increased T cell receptor (TCR) clonal expansion in mucosal and lymphoid sites. Together, our findings identify staged development of memory T cells targeted to tissues during the formative years, informing how we might promote and monitor immunity in children. [Display omitted] • Memory T cells preferentially accumulate in human mucosal tissues during early life • T RM cells undergo functional maturation over childhood • T RM cells exhibit distinct transcriptional programs and site-specific expansion over age Immune memory generation during early childhood is critical for long-term protective immunity. Connors et al. analyze the development of human memory T cells in lymphoid organs, mucosal sites, and blood over infancy and childhood. Memory T cells accumulate rapidly in the intestines and lungs and display age- and tissue-driven maturation stages. [ABSTRACT FROM AUTHOR]