The proliferative activity of astrocytes after immunoglobulin G uptake in the injured mouse cerebral hemisphere

Dividing cells were labeled with [H-3]thymidine injected at different intervals following the injury of the rat cerebral hemisphere. Brain sections were double immunostained for GFAP and for immunoglobulin G (IgG), and subjected to autoradiography. Thereafter, three cell types were counted within the injury area: (1) autoradiographically labeled and (2) unlabeled astrocytes immunopositive both for GFAP and IgG (GFAP+/IgG-), and (3) autoradiographically labeled astrocytes immunopositive exclusively for GFAP (GFAP+/IgG-). Reactive proliferation of GFAP+/IgG- astrocytes began on the Ist day after injury and reached its maximal intensity on day 4, whereas the population of non-proliferating GFAP+/IgG+ astrocytes increased continuously during 8 days after injury and then decreased. Proliferating GFAP+/IgG+ astrocytes were found only occasionally during the whole examined period and did not-display significant quantitative changes. The results suggest that the ability of astrocytes to proliferate after IgG uptake is very low in comparison with those containing no IgG