CD4 and infection: Antibody depletion of CD4+ T cells in PbA-infected F1 (129/Ola X C57BL/6J) (46), CBA/Ca (66), and C57BL/6 mice (39, 64) prevented the development of ECM when conducted before or early in the infection, suggesting an essential role for CD4+ T cells in the initiation of ECM pathogenesis.