Fig. 5

Macrophages Mediate M. leprae Demyelination

(A) TEM from 6 dpi (8 dpf) larva showing M. leprae bacilli (L) within a phagocyte contacting a myelinated axon. Dashed line indicated insets 1 and 2, shown in (B); myelinated axons highlighted in pink; scale bar, 1 μm.

(B) Insets from (A), showing the M. leprae double membrane (arrows) and phagosomal membranes (arrowheads); scale bar, 1 μm.

(C) Rendered still images from a time-lapse movie (Movie S6) of an M. leprae-infected double-transgenic mbp;mpeg1 larva with fluorescent macrophages and myelinating membrane. At 4 days post-fertilization, the larva was infected in the spinal cord and immediately imaged for 12 hr, revealing infected macrophages patrolling intact myelin sheaths (a myelin-patrolling, infected macrophage highlighted in yellow). Scale bar, 10 μm.

(D) Proportion of uninfected (−) or infected (+) macrophages that colocalized with myelin in 4 dpf larvae infected with M. marinum or M. marinum:PGL-1. n = number of macrophages scored.

(E) Mean speed of macrophages in the larvae from (D).

(F) Mean sphericity of macrophages in the larvae from (D).

(G) Mean number of macrophages per infected region in (5 dpf) mbp larvae 2 dpi with M. marinum or M. marinum:PGL-1. Numbers of fish, regions, and macrophages scored per group are indicated.

(H) Mean number of macrophages per region that were both infected and myelin colocalized in the larvae from (G).

(I) Mean number of myelin protrusions per macrophage in the larvae from G. Student’s t test.

(J) Myelin protrusions per M. leprae-infected region in WT mbp larvae (+) or those depleted of macrophages (−) by injection with irf8 morpholino and lipo-clodronate. Student’s t test. Data are representative of at least two separate experiments.

See also Figure S4 and Movies S3, S4, S5, S6, S7, and S8.