ImmGen is an educational tool focusing on gene expression levels in various mouse and human immune system cells. By inputting a gene name or alias in the search bar, users can view a list of hits and swipe through them. The app presents a unique "heatmap barcode" indicating the expression levels of the selected gene across different immune system cell lineages such as B cells, T cells, and Myeloid cells.

Users can switch between three datasets: mouse RNA-seq, mouse microarray, and human RNA-seq, offering comprehensive insights into gene expression. By tapping on a cell lineage icon, users can visualize the expression data through a bar chart. The app also allows toggling between log and linear axis for data visualization preferences.

For a deeper dive, users can explore related genes through the "gene constellation" view, showcasing correlations with key populations within the immune system. ImmGen is a valuable resource developed by the Immunological Genome Project, supported by the National Institutes of Health (NIAID).