AGE-RELATED EXPRESSION PATTERNS OF THE CD15 EPITOPE IN THE HUMAN LATERAL GENICULATE-NUCLEUS (LGN)

The age-related distribution of the trisaccharide epitope 3-fucosyl-N-acetyl-lactosamine (CD15) was evaluated in the human lateral geniculate nucleus (LGN). Coronal paraffin sections from individuals between the 12th week of gestation to 99 years of age were processed for immunohistochemistry using monoclonal antibodies against the CD15 epitope. CD15 immunoreactivity was present in the neuropil from the 14th week of gestation with a graded pattern along the anteroposterior and mediolateral axes of the LGN. Immunoreactivity then became preferentially located within the future cell layers, shortly before cellular segregation was visible in Cresyl Violet stained sections. Maximal CD15 expression occurred from the 22nd week of gestation until the beginning of visual experience (second week of postnatal life). During the subsequent period the spatial pattern of CD15 expression changed. Whereas immunoreactivity in the cell layers gradually disappeared, CD15 positive astrocytes became transiently concentrated in the intercellular layers. The staining within the interlaminar region was best developed at about one year of postnatal life. The adult pattern was found at around 10 years of age, when the LGN appeared almost unstained. Two stages of CD15 expression can thus be separated. The first is characterized by neuropil staining and is synchronized with the time profile of neuronal maturation and of formation of non-stabilized contacts. CD15 is at this time possibly correlated with structural instability and increased vulnerability but at the same time with a high degree of plasticity. The second, peri- and postnatal stage is characterized by CD15 positive astrocytes. These appeared when CD15 in the neuropil disappeared. This loss of CD15 expression in the neuropil occurs during the phase of experience-dependent establishment of the mature interconnectivity and probably heralds loss in plasticity. The time-related expression pattern of CD15 is therefore compatible with the idea that CD15 levels reflect different degrees of developmental determination of retino-geniculate interaction.