Rapid assays for T-cell activation by RNA measurements using flow cytometry

A method for detecting copies of at least one RNA molecule expressed in individual cells or for analysis of gene expression in individual cells by detecting copies of at least one RNA molecule, comprising

• (a) fixing and permeabilizing the cells;
• (b) labeling copies of at least one RNA molecule expressed by the cells with a set of 10-100 fluorescently labeled oligonucleotide hybridization probes that have sequences complementary to the RNA molecule and each is singly labeled with the same fluorescent moiety, and washing away unbound probes, wherein the set of probes bind simultaneously to said RNA molecule;
• and
• (c) detecting, by flow cytometry, cells having expression events, an expression event being one or more fluorescence measurements categorized by fluorescence intensity gating.