THE ANTIGEN SELF-PRESENTATION FUNCTION OF THE CYTOTOXIC T-CELL CLONE 10BK.1 DEPENDS ON RECIPROCAL PEPTIDE PRESENTATION

Cells of the cytotoxic T-cell clone 10BK.1 proliferate in response to ovalbumin (OVA) not only in the presence, but also in the absence, of antigen-presenting cells. This response is the consequence of reciproc al antigen presentation by two 1OBK.1 cells. At the single-cell level, we found antigen-induced changes in the cytosolic Ca2+ concentration ([Ca2+](i)) only in 10BK.1 cells that had contact with another 1OBK.1 cell. This finding suggests that a single cell is unable to present th e antigen to itself, and that two 1OBK.1 cells are necessary and adequ ate to present the antigen to each other. Our data indicate that 1OBK. 1 cells are not capable of processing the OVA molecule. The naturally processed peptide OVA257-264 is a very potent antigen for these cells. A corresponding peptide seems to be present not only in preparations of native OVA, but also in preparations of the commonly used peptide O VA258-276. This 19mer peptide does not bind with high affinity to the relevant K-b class I molecule.