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

Dividing cells were labeled with [3H]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 1st 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.