Thymic and Postthymic Regulation of Naïve CD4⁺ T-Cell Lineage Fates in Humans and Mice Models

Figure 3

Anatomic macroscopic and microscopic structures of a large thymus ((a), (b), (c), and (d)) obtained from an immortomouse at three-month age. The panoramic view shows that the morphology and epithelial and lymphoid structures are preserved. The dense lymphoid tissue in the thymic cortex and medulla areas ((b) and (c)) indicates active germinal centers for T-cell differentiation. The tissues were stained for immunohistochemistry with hematoxylin and eosin (c) and anti-large T-SV40 monoclonal antibody (d). The phenotypic characterization of the thymus and spleen CD4 lineages by fluorescent microscopy analysis of labeled cells ((e), (f), (g), and (h)) and flow cytometric analysis ((j), (k), and (l)) indicated that pre-T-cells progressed through their development to become specific subtypes CD4⁺, CD8, and double-positive CD4⁺/CD8⁺ (j) as observed in the control mice (i). The rates of CD4/Foxp3 expression in T-cell populations expanded 9-fold in the hyperplasic thymus (l) as compared to control (k). All cells were labeled using fluorescein-conjugated anti-mouse CD3, phycoerythrin-conjugated anti-mouse CD4, and allophycocyanin- (APC-) conjugated anti-mouse CD8 mAbs and Alexa 488-conjugated anti-mouse Foxp3 mAbs (BD Biosciences). Numbers refer to percentages of cells in marker region after subtraction of other subpopulations.

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