Figure 4

Massive infiltration of immune cells in sciatic nerves of L31/CD4 ^-/- mice. Cell infiltration in the diseased sciatic nerves was first evidenced by the significant increase of DAPI labelled cell number (A-B). Immunohistochemistry analysis demonstrated that while there was a slight increase of elongated (insert) Iba-1⁺ cells in the pre-symptomatic L31/CD4^-/- mice, nerves from the symptomatic L31/CD4^-/- mice were submerged with round-shaped (insert) infiltrated Iba-1⁺ macrophages (A). While there were abundant CD8⁺ T cells found in the sciatic nerves of symptomatic L31 mice, no CD8⁺ T cell infiltration was detected in pre-symptomatic L31/CD4^-/- mice (B). Quantitative analysis with FACS (n = 3/group) confirmed the immunohistochemistry observation (**: p < 0.01, ***: p < 0.001) (C). In symptomatic L31 mouse sciatic nerves, infiltrates could either group in small foci (D-left) or be distributed diffusely (A/B-right). Fragmented myelin were found within Iba-1⁺macrophages (yellow signals within Iba-1⁺ cells). There were less infiltrates in the area where myelin remained in healthy shape (D-left). Majority of infiltrated Iba-1⁺ macrophages had high levels of B7.2 expression (D-middle) and CD8⁺ T cells were in close apposition with Iba-1⁺ macrophages (D-right). Scale bar: 200 μm.