In August, the journal Nature Aging published a fabulous article about what researchers call immune aging. The thymus, the small organ where a key class of immune cells is trained, starts shrinking at puberty. The first, from Stanford Medicine and published in July in the journal Science, examined two immune cells working in tandem. Aging cells begin exporting structures called R-loops (temporary tangles of DNA and RNA) out of the cell nucleus, where they do not belong. The immune system mistakes them for an invader and sounds an alarm that never shuts off.