CD4 and infection: While the latter group exhibited massively increased numbers MCMV-specific CD4 T cells upon infection and showed increased control of viral replication, CD4 T cell responses in the presence or absence of IL-10Rβ selectively on CD4 T cells resulted in similarly low frequencies of MCMV-specific CD4 T cells as in presence of IL-10Rβ on CD4 T cells, indicating that direct IL-10 signaling on CD4 T cells does not constrain the size of the MCMV-specific CD4 T cell pool (Figure S2 and Text S1).