CD4 and Langerhans cell histiocytosis: The regulatory function of T-regs in granulomas and blood of patients with LCH was suggested by their phenotype (CD4+ CD25high FoxP3high), their intimate contact with LCH histiocytes (Figure 3A), their ability to inhibit T cell proliferation in vitro (see Figures 4B and 5C), the presence of IL10 transcripts in the lesion, and the lack of DTH response in vivo in patients with LCH (see Table 2).