Modulation of accessory molecules on lung T cells.

Stimulation of T cells via the CD3/TCR complex is associated with the reduced expression of accessory molecules, a phenomenon called modulation. To investigate whether the modulation is implicated in the pathogenic mechanism of pulmonary disease, we determined the MFI of CD3, CD4 and CD8 on lung and blood lymphocytes in ten normal subjects and 54 patients with various pulmonary and extrapulmonary diseases. Although there were no significant differences in MFI of these accessory molecules on lung lymphocytes among the groups, MFI of CD3 on lung lymphocytes was significantly decreased compared with that on blood lymphocytes in all groups, demonstrating the modulation of CD3 on lung lymphocytes. Since it has been shown that T cells whose CD3/TCR is modulated are hyporesponsive to various mitogenic signals, our observation seems to represent another aspect of the mechanism whereby the local pulmonary milieu maintains the autoregulation of immune response.