Thy-1-like immunoreactivity in human brain during development.

Thy-1-like immunoreactivity was found in several areas of the immature and adult human brain, using indirect immunofluorescence techniques. In the fetal brain (31 gestational weeks) most immunoreactivity was located in the white matter with an overall granular diffuse distribution and stray fluorescent fibrous structures radiating into grey matter. At 2 months postnatally, the large axon bundles of the internal capsule traversing the caudate nucleus were strongly positive, whereas surrounding neuropil seemed to be negative. In the adult caudate nucleus no such fluorescent fibre bundles could be observed. At 8 months of age, both cerebellum and frontal cerebral cortex contained large numbers of fibrous structures in the grey matter in addition to white matter fluorescence. The molecular layer of both areas was negative. The 8-month-old cerebellum had a Thy-1 distribution similar to the adult, while in the frontal cortex cerebri the density of fluorescent structures increased gradually until adulthood. However, in the 5-year-old frontal cortex the immature granular appearance of 2-month-old cortex could still be seen, but with a greater number of radiating fluorescent bundles. In the adult brain, cerebellum contained a dense pattern of thick, fibrous fluorescent structures in white matter and the internal granular layer and in the frontal cortex thick bundles radiated into grey matter to form a plexus of coarse individual fibres in layers II and III. The hippocampal formation of the 31-week-old fetus contained a network of thin varicose fibres, ascending from the white matter. Stratum radiatum at this stage contained numerous small spots of Thy-1-like immunoreactivity, but no visible fluorescent fibres.(ABSTRACT TRUNCATED AT 250 WORDS)