H2AB1 and viral infectious disease: When comparing the fibroblasts during various perturbed states, fibroblasts isolated from LNs during a viral infection are still the main contributors to the Ccl19 cluster and preferentially express H2‐Ab1 and Cd74, as well as other antigen processing and presentation pathway genes, even when compared with fibroblasts isolated during and after lung viral infections, which are more closely matched inflammatory states (Figure S1).