Transfer of B cells reduces accumulation of CD4⁺ T cells and αSM-actin⁺ smooth muscle cells. (a–c) Immunoperoxidase staining of CD4⁺ T cells in aortic lesions of (a) splenectomized apoE° mice, (b) splenectomized apoE° mice reconstituted with CD4⁺ T cells from atherosclerotic apoE° mice, and (c) splenectomized apoE° mice reconstituted with B cells from atherosclerotic apoE° mice (×100 magnification). Significant infiltrates of CD4⁺ cells are present in a and b but not in c. (d–f) Immunophosphatase staining of αSM-actin in aortic lesions of (d) splenectomized apoE° mice (×100), (e) splenectomized apoE° mice reconstituted with CD4⁺ T cells from atherosclerotic apoE° mice (×200), and (f) splenectomized apoE° mice reconstituted with B cells from atherosclerotic apoE° mice (×100). In (d), an αSM-actin⁺ cap is present in the lesion (arrow), and the media have reduced αSM-actin staining (compare with e and f). In e, the arrow points to αSM-actin⁺ cells in the lesion. In f, only a few intimal cells are discerned (arrow) and there is strong medial αSM-actin staining. (g) Quantification of CD4⁺ T cells. Increased infiltration of CD4⁺ T cells was found in lesions of splenectomized mice, while animals protected by adoptive transfer had fewer infiltrating CD4⁺ cells. Data are expressed as percent of all hematoxylin-stained cells in the lesions. n = 8 (sham), 7 (Sx), 4 (yng E°), 4 (E⁺), 6 (ascl E°), 4 (E° T), 4 (E° B). *P < 0.05 vs. sham.