CAG repeat mutation in the mouse IL-2 gene enables concurrent assessment of T- and B-cell-specific gene expression by northern analysis.

The unique presence of CAG triplet repeats in the mouse IL-2 gene, lending the IL-2 cDNA a second specificity to MHC class II invariant chain (Ii) mRNA, coincides with another unusual genetic feature of the mouse, the lack of Ii gene upregulation in stimulated T cells. While the former anomaly allows simultaneous measurement of IL-2 and Ii mRNAs by Northern analysis, the latter condition ensures that Ii mRNA remains a T-cell-independent, specific marker of Ii positive, primarily B cell function. Thus, Northern analysis using CAG repeat containing IL-2 cDNA enables concurrent assessment of T and B cell activities in the spleen or in other mixtures of mouse lymphocytes.