IMMUNOHISTOCHEMICAL DETECTION OF MYELIN BASIC-PROTEIN IS A SENSITIVE MARKER OF MYELINATION IN 2ND TRIMESTER HUMAN FETAL SPINAL-CORD

The Luxol fast blue (LFB) technique is widely used for the assessment of myelination. Lectin histochemistry using peanut agglutinin (PNA) has also been employed for this purpose. Recently, immunohistochemical methods using antibodies to several myelin-related proteins have been adopted to study myelination in humans. However, the relative sensitivities of these different methods for the detection of early myelination in the human fetal central nervous system have not been determined. Vibratome sections of cervical spinal cord from 15 human abortuses ranging in age from 15 to 24 gestational weeks (GW) were probed with immunohistochemical methods using antibodies to myelin basic protein (MBP), 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), and myelin-associated glycoprotein (MAG). In addition, LFB and PNA histochemistry was employed. The degree of myelination observed in immunohistochemically stained sections was compared to that found in corresponding LFB- and PNA-stained paraffin-embedded tissues. The intensity of myelination was graded by two observers on a scale of 0 (none), + 1 (mild), + 2 (moderate), and + 3 (marked). At all ages examined, the MBP immunohistochemical method revealed more myelin than LFB or MAG staining. CNPase could not be reliably detected until after 18 GW. Peanut agglutinin stained myelin, but subpial astrocytes and the intervening neuropil were also stained. These results suggest that MBP is a more sensitive marker for early human fetal myelination than CNPase, MAG, PNA or LFB.