Generic method for imaging transgene expression

We propose a generic method to report on gene expression based on the use of an antigen–antibody reporting system and visualization by MRI. This methodology was demonstrated using a truncated form of the H2K k antigen, t H2K k , as the nonendogenous antigen to be imaged. HeLa cells, transfected to express t H2K k , exposed to t H2K k antibodies conjugated to a superparamagnetic iron oxide particle, generated strong negative contrast compared to non‐H2K k expressing cells by MRI. T 2 of the t H2K k expressing cells was 57.6 ± 17.0 ms, compared to 424.0 ± 38.7 and 445.4 ± 47.2 ms for the mock transfected and nontransfected cells, respectively ( P < 0.001). t H2K k expression in the former cells was confirmed by flow cytometry, fluorescence, and electron microscopy. The methodology can be adapted to image in vivo other nonendogenous antigens in cells/tissues. Magn Reson Med 54:218–221, 2005. © 2005 Wiley‐Liss, Inc.