Increasing level of CD56+ T-cells in peripheral blood in sarcoidosis.

We read with interest the recent paper by KATCHAR et al. [1] reporting the characterisation of natural killer (NK) cells and CD56+ T-cells in sarcoidosis patients. The authors observed that, in the lung of patients with pulmonary sarcoidosis, NK cells have a distinct phenotype. They produce cytokines and participate actively in the T-helper (Th)-1-like inflammatory response. In addition, although they did not find any difference in the NK cell number between sarcoidosis patients and control subjects, the authors found an elevation of CD56+ T-cells in the peripheral blood (PB) of sarcoidosis patients. CD56+ T-cells are large granular lymphocytes with a significant proportion of CD4-CD8cells or cd T-cells, and, to our knowledge, this is the first study in which such expansion of CD56+ T-cells in PB is described in sarcoidosis.