ENHANCED T-CELL PROLIFERATION AND INCREASED RESPONDER FREQUENCY FOLLOWING DELIVERY OF ANTIGEN TO THE ANTIGEN-PRESENTING CELL - B-CELL DEPENDENCY AND USE IN DETECTION OF AUTOREACTIVE T-CELLS

Reported frequencies of peripheral blood autoantigen-specific cells in autoimmune diseases are typically low, which could be due to true sca rcity or to limitations of in vitro assays. In the present study, anti gens were targeted to the antigen-presenting cell (APC) to enhance T c ell proliferation, using an antigen delivery system (ADS), consisting of biotinylated anti-IgG, streptavidin and biotinylated antigen. This was able to bind B cells and monocytes and was internalized within 24 hours. T cell proliferation to tetanus toroid was at least doubled usi ng the ADS compared to conventional assay with antigen in simple solut ion. To evaluate the ADS in an autoimmune disease, we determined T cel l responses to the insulin-dependent diabetes mellitus (IDDM)-associat ed autoantigen IA-2ic in patients with recent-onset IDDM. When IA-2ic was available conventionally in solution, proliferation was poor, but significantly higher in IDDM patients than control subjects. However, the ADs significantly enhanced proliferation by a mean 3-fold for all subjects, while maintaining the significant difference between IDDM pa tients and healthy controls. Increases in T cell proliferation via the ADS were due to the recruitment of approximately 3 times the number o f CD4 + T cells stimulated in conventional assays. B cell depletion ab olished enhancement suggesting that the ADS operates through recruitme nt of B cells as APCs. This flexible modification of the T cell assay offers greatly enhanced sensitivity for determining the frequency of a ntigen and autoantigen-reactive T cells. (C) 1998 Published by Elsevie r Science B.V. All rights reserved.