The similar expression pattern of MHC class I molecules in human and mouse cerebellar cortex.

The major histocompatibility complex (MHC) class I molecules are considered to be important in the immune system. However, the results reported in the past decade indicate that they also play important roles in the central nervous system. Here we examined the expression of MHC I and β2-microglobulin (β2m) in human and mouse cerebellar cortex. The results show that MHC I molecules are expressed both in human and mouse cerebellar cortex during brain development. The expression of H-2K(b)/D(b) is gradually increased with the development of mouse cerebellar cortex, but finally decreased to a very low level. Similarly, the expression of HLA-B/C genes is increased in developing human cerebellar cortex, but decreased after birth. The spatial and temporal expression of β2m overlaps mostly with that of HLA-B/C molecules, and they are co-expressed in Purkinje cells. Our findings provide a fundamental basis to reveal the functions of neuronal MHC class I molecules in the development of human cerebellum.