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 reciprocal antigen presentation by two 10BK.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 10BK.1 cell. This finding suggests that a single cell is unable to present the antigen to itself, and that two 10BK.1 cells are necessary and adequate to present the antigen to each other. Our data indicate that 10BK.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 OVA258-276. This 19mer peptide does not bind with high affinity to the relevant Kb class I molecule.