Figure 1.

APAAP immunohistochemical detection of CD200 expression in retina of CD200^+/+ and CD200^−/− mice. A: CD200 is abundantly expressed on endothelium (E) (arrowhead) and neuronal axons and cell bodies in CD200^+/+mouse (N) (arrow) normal retina but is expectedly absent in CD200^−/− mice (B). C: MG (defined by CD45⁺CD11b⁺ population by two-color flow cytometric analysis) are present in significantly greater numbers within CD200^−/− retina (n = 7, P = 0.04). Results shown are percentages of total events collected. Unlike CNS and rat retina, 23 mouse retinal MG and macrophages express equivalent levels of CD45, and cannot therefore be differentiated by CD45^low or CD45^high, respectively. Original magnifications: ×250 (A); ×300 (B).