In comparison to FV-infected Rag1−/− recipients of EF4.1 TCRβ-transgenic CD4+ T cells, anemia development in FV-infected Rag1−/−Ifngr1−/− recipients was absent or markedly delayed, demonstrating an essential role for IFN-γ signaling in this process (Figure 4F). This evidence concerns the gene CD4 and anemia (phenotype).