Premature mortality in mice with Socs1 gene inactivation in lymphoid and myeloid lineages. (A) Cre expressed under the lysozyme promoter (LysM-cre) deletes Socs1^lox in both lymphoid and myeloid lineages. Socs1^lox recombination switches on an hCD4 reporter within the targeted locus, and thus recombination was tracked by analyzing hCD4 expression by flow cytometry. Shown are leukocyte populations (□, Socs1^lox/+ nontransgenic; ▦, Socs1^lox/+cre) in the spleen and blood. Cells were stimulated with 100 U/mL IFN-γ for 4 hours to increase hCD4 reporter activity. As a positive control, CMV-cre was used to delete Socs1^lox during embryogenesis, and therefore in all cells. The percentage of hCD4⁺ cells is indicated in each histogram. (B) Survival curves of Socs1^lox/-LysM-cre (•; n = 28) and littermate control Socs1^lox/- nontransgenic (▪; n = 21) mice.