Nf1 homozygosity results in increased thymic T-cell subset numbers but reduced T-cell receptor–mediated proliferation.

(A) Comparison of cells in each major T-cell subset between WT cells transplanted into RAG2^−/− mice (WT→RAG2^−/−) and Nf1^−/− cells transplanted into RAG2^−/− mice (Nf1^−/−→RAG2^−/−) thymus. Bars represent the absolute numbers of indicated T-cell subsets (± SEM), n = 13 and * P < .001. (B) Immunocytometric analysis of thymocytes from WT→RAG2^−/− andNf1^−/−→RAG2^−/− mice. Cells were stained with fluorochrome-conjugated antibodies directed against the indicated cell surface proteins and analyzed by flow cytometry. Data are representative of 5 independent experiments with similar results. (C) Reduced proliferation of Nf1^−/−thymocytes. Thymocytes (10⁵/well) were isolated and activated with plate-bound anti-CD3 mAb or anti-CD3 mAb plus IL-2. Proliferation was measured by thymidine incorporation assay. Bars denote the mean thymidine incorporation (cpm ± SEM) of a representative experiment performed in replicates of 6. * P < .01 Nf1^−/− versus WT. ** P < .01 Nf1^−/− versus WT.