Objective: We examined the reduction of T cell receptor (TCR) AV24+,BV11+ CD4-,CD8- (double-negative [DN]) natural killer T (NKT) cells in peripheral blood lymphocytes (PBLs) from patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and Sjogren's syndrome (SS) to analyze why NKT cells are selectively reduced in autoimmune diseases, and to examine whether nonresponse to alpha-galactosylceramide (alpha-GalCer) is due to an abnormality in the antigen-presenting cells (APCs) or NKT cells.
Methods: Peripheral blood from patients with RA (n = 20), SLE (n = 18), SSc (n = 13), and SS (n = 17), as well as from healthy donors (n = 13) and patients with Behçet's disease (BD; n = 20), was examined by flow cytometry to determine the number of TCR AV24+,BV11+ DN T cells. PBLs from 10 RA, 10 SLE, 8 SSc, and 9 SS patients, as well as from 7 healthy subjects, were cultured in vitro with alpha-GalCer, and the number of TCR AV24+,BV11+ DN NKT cells was estimated. APCs from responder and nonresponder patients were cocultured with NKT cells from responder and nonresponder patients.
Results: The mean +/- SEM number of TCR AV24+,BV11+ DN NKT cells per ml of whole blood was found to be 48.8+/-10.0 in RA patients, 50.6+/-12.9 in SLE patients, 80.8+/-30.6 in SSc patients, and 40.0+/-11.7 in SS patients, while 290.0+/-69.6 and 321.2+/-103.4 NKT cells were present in healthy subjects and BD patients, respectively (P < 0.01). Three of 10 RA patients, 5 of 10 SLE patients, 4 of 8 SSc patients, and 6 of 9 SS patients (a total of 18 of 37 patients, or 48.6%) responded to alpha-GalCer, indicating that patients could be divided into two groups: alpha-GalCer responders and nonresponders. In contrast, NKT cells from all healthy subjects proliferated against alpha-GalCer. APCs from all nonresponder patients were found to function as alpha-GalCer-presenting cells, while NKT cells from nonresponders did not expand even in the presence of APCs from normal responders.
Conclusion: These findings strongly suggest that patients with autoimmune diseases can be divided into two groups (alpha-GalCer responders and nonresponders). They also suggest that the reduced numbers of NKT cells in patients with autoimmune diseases may be due to an inadequate amount of alpha-GalCer-like natural ligands (i.e., adequate in only 48.6% of patients) for the induction of NKT cells in vivo, or to a dysfunction in the NKT cells themselves (in 51.4% of patients).