C57bl 6 inbred mice

Twelve-week-old male and female C57BL/6 inbred mice were purchased from Charles River (Barcelona, Spain) and shipped to our animal facility (UBIOMEX, PRBB) to be used as breeders. On arrival, they were housed in standard cages at constant temperature (21°C ± 1°C ) and humidity (55% ± 10%) under a reversed light-dark cycle (white lights on 8:00 pm-8:00 am). After 1 week of acclimatization, breeding pairs were mated, and pregnant females were observed daily for parturition. For each litter, the date of birth was designated as postnatal day (PND) 0. Pups remained with their mothers for 21 days and were then weaned (PND 21). After weaning, male offspring were used for other experiments, and female mice from each litter were randomly assigned to the different diets to avoid potential litter effect. All animal care and experimental procedures were approved by the local ethics committee (CEEA-PRBB) and conducted in accordance with the European Union Directive 2010/63/EU guidelines on the protection of animals used for scientific purposes. ARRIVE guidelines for reporting animal research have been followed.

For T cell transfer experiments, female B6.129S7-Rag < tm1Mom>/J [RAG1^-/-] mice were purchased from Jackson Laboratories [Bar Harbor, ME, USA] and further bred in the animal facility of the Academic Medical Center [AMC], Amsterdam. As wild type donors, female C57BL/6 inbred mice were purchased from Charles River Laboratories [Maastricht, The Netherlands]. For in vitro and subsequent transfer experiments, two different TYK2-deficient mice were provided by the University of Veterinary Medicine, Vienna, Austria: mice carrying a point mutation in the TYK2 kinase domain [TYK2^K923E; termed henceforward TYK2^KE] resulting in abrogated kinase activity, as has been shown previously.^{29 (link),30 (link)} In addition, we were provided with mice carrying a targeted disruption of the TYK2 gene by placement of a neomycin resistance gene cassette [termed TYK2^KO].^{15 (link)} For the second transfer experiment, TYK2^KE mice were back-crossed into RAG1^-/- mice for three generations. Animals were housed in individually ventilated cages at the AMC’s laboratory animal facilities. In all transfer experiments, acceptor and donor mice were age-matched [8–12 weeks] and gender-matched [female]. Animals were maintained on a 12/12 light/dark cycle under conditions of constant temperature [20°C ± 2°C] and humidity [55%] and were supplied with water and chow ad libitum.