Table 2. Abundance and phagocytic activity of myeloid cells in demyelinated lesions.
| 1 week | 6 weeks | |||
|---|---|---|---|---|
| Cells in 0.1mm2 | % cells with phagocytosed MBP | Cells in 0.1mm2 | PDGFRβ + | |
| Cells in 0.1mm2 | ||||
| WT-WTBM | ||||
| Iba-1+/ F4/80+/ EGFP+ Mac | 111 ± 14.4 | 27 ± 3% | 6.29 ± 1.5 | 0 ± 0 |
| Iba-1+/ F4/80+/ Microglia | 11.63 ± 2 | 45 ± 7% | 3.26 ± 0.9 | 0 ± 0 |
| KO-WTBM | ||||
| Iba-1+/ F4/80+/ EGFP+ Mac | 72.9 ± 12.6* | 36 ± 3%* | 7.67 ± 1.3 | 0 ± 0 |
| Iba-1+/ F4/80+/ Microglia | 11.34 ± 1.8 | 25 ± 6%* | 3.95 ± 1.2 | 1.46 ± 0.3*** |
| WT-KOBM | ||||
| Iba-1+/ F4/80+/ EGFP+ Mac | 21.73 ± 2.5*** | 13 ± 4%** | 18 ± 2.9** | 5.26 ± 1*** |
| Iba-1+/ F4/80+/ Microglia | 59.64 ± 13*** | 30 ± 3%* | 10.24 ± 1.2** | 2.01 ± 0.3*** |
Numbers of Iba-1+/ F4/80+/ EGFP+ macrophages and Iba-1+/ F4/80+/ EGFP- microglia were determined per 0.1 mm2 area in lesions at 1-week and 6-weeks after demyelination. At 6-weeks, numbers of PDGF-R beta (PDGF-Rβ+) expressing macrophages and microglia were also determined. Values represent means ± S.D. Statistically significant differences are indicated by
* < 0.05
** < 0.01
*** < 0.001 for values compared to WT-WTBM macrophages or microglia at the same post-injection week. Additional immunostaining for MBP allowed determination of the percentage of macrophages and microglia that had phagocytosed myelin debris. Percentage of phagocytic macrophages = MBP+Iba-1+EGFP+/ Iba-1+EGFP+ x 100. Percentage of phagocytic microglia = MBP+Iba-1+EGFP-/Iba-1+EGFP- x 100. Essentially identical results were obtained when F4/80 was used as the myeloid cell marker. Because our engraftment efficiency is around 95% in each of the chimeric mouse lines (see Table 1), a few surviving recipient macrophages will be mistakenly scored as EGFP-negative microglia in each of these trials. Microglial abundance is therefore slightly inflated in all cases.