DIFFERENTIAL APC REQUIREMENTS OF SELF-REACTIVE AND NONSELF-REACTIVE T-CELLS AND T-CELL-HYBRIDOMAS SPECIFIC FOR RETINAL S-ANTIGEN

Autoreactive T cell hybridomas specific for pathogenic peptides of ret inal S-Ag require a novel radiosensitive APC activity for IL-2 secreti on that is distinct from Ag presentation by MHC class II. Antigen-depe ndent IL-2 secretion by self-reactive hybridomas was much more efficie nt with splenic APC than with thymic APC, although both provided simil ar levels of hybridoma TCR occupancy as measured by activation-induced cell death. Furthermore, thymic APC did stimulate IL-2 secretion by a non-self reactive hybridoma. To test the hypothesis that this activit y was provided by a distinct cell population, fractionated splenocytes were tested for their ability to present Ag to these hybridomas. The most potent Ag presentation for IL-2 secretion was found to segregate with low-density, B cell-enriched fractions while adherent cells, or p urified T cells were unable to support IL-2 production. Together with previous results, the data show that antigen presentation leading to I L-2 secretion by these autoreactive T cell hybridomas requires activat ed B cells, whereas TCR occupancy can be provided by several APC subse ts.