Secretomers as a new tool for the monitoring of CTL responses

Efforts to follow tumor-specific immune responses in patients are often thwarted by lack of knowledge of the appropriate tumor antigens and the CTL epitopes of those antigens. There is, therefore, a growing need for techniques to monitor tumor-specific immune responses in settings where tumor antigens, and antigenic epitopes, remain unidentified. Here we describe a novel system to follow tumor-specific CTL immune responses. A truncated, soluble murine class I MHC (H-2D^b) molecule was fused with a rat IgG_2a Fc, in order to allow secretion of the complex. Tumor-specific CTL could then be detected as a result of the complex fastening to specific T cell receptors (TCR). These constructs were inserted into the genome of a recombinant adenovirus vector. Infection of tumor cells with these adenovirus constructs results in the secretion of the complexes into the culture supernatant. These soluble divalent class I MHC molecules were used to detect and activate specific CTL populations.