Interestingly, in the late phase of infection, both spleen and lymph nodes comprised FV-mWasabi-infected cells that were not overlaid by any of the cell subsets and were indeed negative for IgD and IgM (population in the lower middle of the t-SNE plot in Fig. 4A); furthermore, as these cells were CD19+ CD93−, we suggest that these cells were mature B cells that have undergone immunoglobulin class switching. Here, CD19 is linked to infection.