Development of the blood-CSF barrier.

The development of the blood-CSF barrier was investigated by establishing total protein, individual protein levels and cell-counts in the CSF and serum of 185 healthy children, with an age range from 27 fetal weeks to 16 years. Albumin, alpha 2-macroglobulin and immunoglobulin G were found in all CSF specimens. With the exception of IgG, their concentrations decreased continuously until the end of the first year of life. IgM was not present in the CSF and IgA was found in only a few cases. Serum:CSF ratios of individual proteins increased continuously from the fetal period to the first year and there was a decline in barrier selectivity during the same period. Maturation of the barrier was maximal during the third month of life, decreasing quickly thereafter. The barrier condition of preterm infants was closely related to conceptional age, but not to the time of birth.