Steady-state, therapeutic, and helminth-induced IL-4 compromise protective CD8 T cell bystander activation.

Memory CD8 T cells (T) can be activated into innate-like killers by cytokines like IL-12, IL-15, and/or IL-18; but mechanisms regulating this phenomenon (termed bystander activation) are not fully resolved. We found strain-intrinsic deficiencies in bystander activation using specific pathogen-free mice, whereby basal IL-4 signals antagonize IL-18 sensing. We show that therapeutic and helminth-induced IL-4 impairs protective bystander-mediated responses against pathogens.

Collaboration between IL-7 and IL-15 enables adaptation of tissue-resident and circulating memory CD8 T cells.

Interleukin-7 (IL-7) is considered a critical regulator of memory CD8 T cell homeostasis, but this is primarily based on analysis of circulating and not tissue-resident memory (T) subsets. Furthermore, the cell-intrinsic requirement for IL-7 signaling during memory homeostasis has not been directly tested. Using inducible deletion, we found that loss had only a modest effect on persistence of circulating memory and T subsets and that IL-7Rα was primarily required for normal basal proliferation.

Axotomy results in an increase in Thy-1 protein in the 35-day-old rat supraoptic nucleus.

We demonstrated previously that the hypothalamic supraoptic nucleus (SON) undergoes an axonal sprouting response following a unilateral lesion of the hypothalamo-neurohypophysial tract in a 35-day-old rat to repopulate the partially denervated neural lobe (NL). However, no sprouting occurs following the same injury in a 125-day-old rat. We previously reported a significant increase in Thy-1 protein in the SON of a 125-day-old rat compared to a 35-day-old rat in the absence of injury.

Responsiveness to interleukin-15 therapy is shared between tissue-resident and circulating memory CD8 T cell subsets.

Interleukin-15 (IL-15) is often considered a central regulator of memory CD8 T cells, based primarily on studies of recirculating subsets. However, recent work identified IL-15-independent CD8 T cell memory populations, including tissue-resident memory CD8 T cells (T) in some nonlymphoid tissues (NLTs). Whether this reflects the existence of IL-15-insensitive memory CD8 T cells is unclear.

Age-dependent increase in Thy-1 protein in the rat supraoptic nucleus.

Mature mammalian CNS neurons often do not recover successfully following injury. To this point, unilateral lesion of the hypothalamo-neurohypophysial tract results in collateral sprouting from uninjured axons of the supraoptic nucleus (SON) in 35-day-old but not in 125-day-old rats. Thus, it appears that there are age-related changes within the SON that preclude the older rat from recovering following axotomy.