Functional heterogeneity of the right and left cerebral neocortex in the modulation of the immune system.

The cerebral neocortex is now known to modulate the immune system but this modulation is hemispherically asymmetrical. It was previously reported that large ablation, including the anterior prefrontal part of the left cortex decreased whereas symmetrical right lesions enhanced B and T cell-mediated responses. However, the neocortex is an heterogeneous structure from anatomical and physiological points of view and it could be speculated that different aspects of the immune system could be regulated by various cortical areas. In these experiments, restricted neocortical lesions involving the parieto-occipital lobes were performed in C3H/He mice. Animals with right lesions showed depressed mitogen-induced lymphoproliferation and enhanced antibody production to sheep erythrocytes as compared to that of animals with bilateral lesions. Left lesions appeared not to modify these reactions. Furthermore, the percentage of suppressor/cytotoxic T lymphocytes was depressed more in animals with bilateral lesions as compared to any of the other groups. None of the lesions performed appeared to modify the natural killer cell activity. These results confirm that connections between left and right cortex are involved in the modulation of the immune system and suggest that the immunomodulatory functions of the cortex depend upon the specific regions within the right cortex.