A role for endogenous transforming growth factor beta 1 in Langerhans cell biology: the skin of transforming growth factor beta 1 null mice is devoid of epidermal Langerhans cells

Abstract

Transforming growth factor beta 1 (TGF-beta 1) regulates leukocytes and epithelial cells. To determine whether the pleiotropic effects of TGF-beta 1, a cytokine that is produced by both keratinocytes and Langerhans cells (LC), extend to epidermal leukocytes, we characterized LC (the epidermal contingent of the dendritic cell [DC] lineage) and dendritic epidermal T cells (DETC) in TGF-beta 1 null (TGF-beta 1 -/-) mice. I-A+ LC were not detected in epidermal cell suspensions or epidermal sheets prepared from TGF-beta 1 -/- mice, and epidermal cell suspensions were devoid of allostimulatory activity. In contrast, TCR-gamma delta + DETC were normal in number and appearance in TGF-beta 1 -/- mice and, importantly, DETC represented the only leukocytes in the epidermis. Immunolocalization studies revealed CD11c+ DC in lymph nodes from TGF-beta 1 -/- mice, although gp40+ DC were absent. Treatment of TGF-beta 1 -/- mice with rapamycin abrogated the characteristic inflammatory wasting syndrome and prolonged survival indefinitely, but did not result in population of the epidermis with LC. Thus, the LC abnormality in TGF-beta 1 -/- mice is not a consequence of inflammation in skin or other organs, and LC development is not simply delayed in these animals. We conclude that endogenous TGF-beta 1 is essential for normal murine LC development or epidermal localization.

Figure 1

TGF-β1 −/− mice lack epidermal LC. Epidermal cell suspensions were prepared from the trunk skin of 17-d TGF-β1 −/− and littermate control mice, stained for CD45 and I-A antigens (or CD45 and TCR-γδ), and analyzed using multicolor flow cytometry. Nonviable cells were excluded during data acquisition. Markers were adjusted such that cells stained with isotype control reagents were contained within the left lower quadrant of each panel.

Figure 2

TGF-β1 −/− epidermis is deficient in allostimulatory activity. Epidermal cells from the trunk skin of TGF-β1 −/− and +/+ mice were incubated with BALB/c lymph node T cells (2 × 10⁵/well) in flatbottomed microtiter plates for 120 h. [³H]TdR was added (1 μCi/well) for the last 12 h of the incubation. Cell-associated radioactivity was measured by direct β counting. Closed circles, epidermal cells from TGF-β1 −/− mice; closed squares, epidermal cells from +/+ controls.

Figure 3

Lymphoid dendritic cells are present in TGF-β1 −/− mice. Frozen sections of axillary lymph nodes from a 14-d TGF-β1 −/− mouse and a +/+ littermate control were stained with several lineage-selective markers using a three-step immunohistochemical technique. (a–d) sections from littermate control. (e–h) sections from TGF-β1 −/− mouse. (a and e) anti-gp40 (G8.8). (b and f  ) anti-CD11c (N418). (c and g) anti-CD3ε (145-2C11). (d and h) anti-macrophage (F4/80).

Figure 4

Rapamycin abrogates the fatal wasting syndrome that results from TGF-β1 deficiency. Progeny of TGF-β1 +/− × +/− matings were treated with rapamycin (4 mg/kg i.p.) on postnatal day 10 and 3×/ wk thereafter. Serial weights were determined before each treatment and representative data are depicted.