Cell‐microarray analysis of antigen‐specific B‐cells: Single cell analysis of antigen receptor expression and specificity

Abstract The authors previously developed a cell‐microarray system that effectively detects antigen‐specific B‐cells by monitoring intracellular Ca 2+ at single cell levels. Here they present a novel method to detect antigen‐specific B‐cells using cell‐microarray system. To detect antigen‐specific B‐cells, they arrayed live lymphocytes on a chip, stained cells with fluorescence‐labeled nonspecific proteins, and analyzed them with a fluorescence scanner to detect nonspecific protein binding to B‐cells. They then stained cells with fluorescence‐labeled antigen and analyzed them with the scanner. Cells stained with specific antigen, but not with nonspecific proteins, were determined as antigen‐specific B‐cells and harvested. Antibody cDNA was amplified from retrieved B‐cells by single‐cell RT‐PCR, inserted into expression vectors, and was examined for its specificity by ELISA. They could detect antigen‐specific B‐cells at a frequency of 0.01% in a model system using transgenic mice that express antibody to hen‐egg lysozyme on the surface of B‐cells. They applied this system to directly detect hepatitis B virus surface‐antigen (HBs‐Ag)‐specific B‐cells from peripheral blood in HBs‐Ag‐vaccinated volunteers and succeeded in producing HBs‐Ag‐specific monoclonal antibody. This novel system allows us to identify human antigen‐specific B‐cells of very low frequency and is a powerful tool to explore the candidates of antibody therapeutics. © 2007 International Society for Analytical Cytology