INCREASED GAMMA DELTA-POSITIVE T-CELLS IN BLOOD AND BRONCHOALVEOLAR LAVAGE OF PATIENTS WITH SARCOIDOSIS AND HYPERSENSITIVITY PNEUMONITIS/

A small population of T cells does not express the conventional T-cell receptor (TCR), characterized by the alpha and beta polypeptide chain s (alpha/beta TCR) but two polypeptides termed gamma and delta (gamma/ delta TCR). Changes in gamma/delta TCR expression may be relevant as t he cause or consequence of several diseases. Our study was undertaken to determine and compare the distribution of T-cells expressing gamma/ delta TCR in blood and bronchoalveolar lavage (BAL) of patients with s arcoidosis, hypersensitivity pneumonitis (AP), idiopathic pulmonary fi brosis (IPF), and of healthy controls. In addition, the association be tween gamma/delta TCR of blood T-lymphocytes and accessory molecules w as analysed. Using direct immunofluorescence with the anti-gamma/delta TCR and anti-CD3 monoclonal antibodies (MoAbs) followed by now cytome tric analysis, the blood of patients with pulmonary sarcoidosis, HP, I PF and of healthy controls was analysed. To reveal the association bet ween gamma/delta TCR of blood T lymphocytes and the accessory molecule s, expression of CD4, CD8 and CD25 were determined. Calculating the pe rcentage and the total number of CD3+ gamma/delta TCR cells hn blood, the data indicated a significant increase of gamma/delta T-cells in in dividuals with pulmonary sarcoidosis and HP, compared to healthy contr ols and IPF patients. In sarcoidosis patients with elevated CD3+ gamma /delta TCR levels, significantly lower CD4/CD8 ratios were observed. I n addition, our data demonstrate a correlation between the decrease of CD4+ cells in blood and the amplified appearance of gamma/delta TCR e xpression in sarcoidosis patients, but not in HP patients. gamma/delta TCR I cells were either CD8-positive (approximately 50%), or had a '' double-negative phenotype'' (CD4-/CD8-) (remaining 50%). Circulating b lood gamma/delta T-cells were CD25-negative, suggesting a lack of acti vation. The total number of CD3+ gamma/delta TCR+-bearing lymphocytes in BAL fluid was increased in sarcoidosis and HP, compared with IPF. A corresponding increase of CD3+ gamma/delta TCR+ cells was observed in blood and BAL of sarcoidosis patients. In conclusion, our data indica te that levels of gamma/delta T-cells are increased in blood and BAL f luid of patients with sarcoidosis and HP. Although this suggests a pat hogenetic role for gamma/delta TCR, it is not clear whether its expres sion is a causal factor, or a consequence, of these diseases.