Presence of circulating abnormal CD34+ progenitors in adult Langerhans cell histiocytosis

Abstract

Langerhans cell histiocytosis (LCH) is related to the proliferation of cells, which are similar to Langerhans cells (LC) but possess many abnormal characteristics. Lesions are widespread and this fact suggests that LCH cells or their precursors are present in the blood of patients. In five adult patients, we have isolated and cultured CD34+ blood progenitors of dendritic cells. We studied their phenotype by flow cytometry and their functional properties in mixed culture with heterologous lymphocytes and with autologous lymphocytes in the presence of tri-nitro-phenyl antigen (TNP). The amount of CD34+ precursors was dramatically higher than controls but a high mortality occurred during the in vitro differentiation. The phenotype of surviving cells was similar to LC phenotype (CD1a+, CD83+, Lag+) but some of them expressed CD2. These cells were able to induce T cell proliferation in mixed culture. They could not initiate primary response to TNP, except in a patient treated with thalidomide. In our hands, these CD34+ cells may be precursors of LCH cells.

Fig. 1

(a,b,c) Observation at day 6 by phase contrast microscopy with a magnification coefficient of 200. Aggregate of dendritic cells (DC) (a); and isolated adherent DC (b and c). (d,e,f) Immunoenzymatic labellings with fuchsin red of day 12 DC. (d,e) Staining with anti-Lag, mag. × 600. (f) Staining with anti-CD2, mag. × 400.

Fig. 2

Total number of cells during the differentiation of CD34⁺ progenitors in dendritic cells. (a) CD34⁺ cells were isolated from 40–70-ml samples of cord blood. (b) CD34⁺ cells were isolated from 450-ml samples of peripheral blood of healthy volunteers. (c) CD34⁺ cells were isolated from 40–70-ml samples of peripheral blood of Langerhans cell histiocytosis (LCH) patients (numbers with arrow identify the two blood samples from patient 1).

Fig. 3

Proliferation of T lymphocytes induced by allogeneic dendritic cells (DC) or DC treated with tri-nitro-phenyl antigen (TNP). Different combinations of cells were used: untreated patients' DC (○) or treated with TNP (□); cord blood-derived DC untreated (•) or treated with TNP (▪); and T lymphocytes from patients (–––––) or from cord blood (—–). The same results were observed with DC generated from peripheral blood or controls (data not shown).