CD4 and Langerhans cell histiocytosis: Thus, although we agree that adoptive cell therapy with T cell receptor-engineered BRAFV600E-specific CD4+ T cells may offer great therapeutic potential, the clinical impact of potentially present BRAFV600E-specific CD4+ T cells in HLA-DQB1*03 bearing, BRAFV600E mutated LCH-patients is questionable.