Kinetic analysis of Ia expression on T cells in patients with systemic lupus erythematosus.

An increased proportion of Ia positive circulating T cells was observed in patients with systemic lupus erythematosus (SLE) (17.2 +/- 5.8%, n = 20, p less than 0.005), compared with normal subjects (3.2 +/- 0.9%, n = 10) by the analysis with flow cytometry using OKIa1. There was a significant difference (p less than 0.05) in the proportion of Ia positive T cells (Ia +T cells) between inactive patients (19.6 +/- 5.8%, n = 12) and active patients (13.6 +/- 3.7%, n = 8). The kinetic analysis in normal subjects revealed that Ia expression on T cells stimulated with Concanavalin A (ConA) was significantly increased on day 4 (10.2 +/- 6.2%, n = 8). However, when stimulated with native DNA from calf thymus (nDNA), Ia expression was not increased (1.4 +/- 1.6%, n = 8). In SLE patients, initial Ia expression faded out within 4 days without stimulus (3.9 +/- 4.0%, n = 10). In spite of the decline of Ia expression with stimulation of both Con A and nDNA, the initial proportion of Ia positive T cells was relatively well maintained with the stimulation of nDNA (16.2 +/- 4.7%). Further analysis of T-cell subpopulations in SLE patients revealed that both OKT8- (T4) and OKT4- (T8) cells expressed Ia antigens. Interestingly, in 4 out of 5 patients with active disease, the incidence of Ia expression in OKT4- cells was increased with nDNA stimulation. Thus, in patients with SLE, circulating Ia positive T cells might be activated in vivo, and be implicated in the development of autoimmunity to DNA.