Identifying novel populations associated with trained immunity and their role in limiting infection

Trained immunity is the recently discovered phenomenon where cells belonging to the innate immune system, despite established wisdom, can display specific and non-specific “memory” after certain immunological challenges. Studies involving the BCG vaccine, initially developed for tuberculosis protection, has uncovered mechanisms that confer resistance to other pathogens, creating a primed state in PBMCs such as monocytes that can last for years. However, all data generated thus far to analyze the transcriptional, epigenetic, and metabolic profiles of trained cells has mostly been limited to bulk analysis. As a result, it remains unknown whether all immune cells are capable of training, what sub-populations emerge as a result, and whether a distinctive training marker can be isolated. We address these questions by isolating splenocytes from trained mice, before and after secondary immune challenges, followed by single cell RNA-Seq, exposing training heterogeneity in the population.