Ruxolitinib but not pacritinib blocks T-cell infiltration into the skin, inhibits evasion of CD4⁺ T cells out of the thymus, and inhibits Stat3/5 phosphorylation. GFP or ITK-SYK mice were treated with vehicle, ruxolitinib, or pacritinib for 32 days, euthanized, and analyzed as described in Figure 4. (A) Immunohistochemical HRP-DAB staining with anti-CD3 antibody (T cells) of paraffin-embedded skin tissue of GFP and ITK-SYK mice after treatment with vehicle (Veh), ruxolitinib, or pacritinib for 32 days. (B) Percentages of T cells, granulocytes, and monocytes within total thymus cells of GFP and ITK-SYK mice after treatment with vehicle or ruxolitinib for 32 days. (C) Percentage of CD90⁺CD4⁺ (CD4⁺) and CD90⁺CD4⁺CD8⁺ (CD4⁺CD8⁺) cells within GFP⁺ thymus cells of GFP and ITK-SYK mice after treatment with vehicle, ruxolitinib, or pacritinib for 32 days. (D) Mean fluorescence intensity for intracellular FACS staining of phosphorylated STAT3 in total CD3⁺CD90⁺ thymic T cells, CD4⁺ T cells, CD8⁺ T cells, and CD4⁺CD8⁺ T cells from treated control/GFP or ITK-SYK mice within GFP⁺ and GFP^– T cells. Bars represent mean values with error bars showing the SEM. Statistical significance was calculated using the Student unpaired t test. ∗P < .05, ∗∗P < .01, ∗∗∗P < .001.