Gamma interferon, but notMycobacterium leprae, induces major histocompatibility class II antigens on cultured rat Schwann cells

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Abstract
In order to investigate the possible role of Schwann cells in immune reactions, and in particular their involvement in the response to infection withMycobacterium leprae, it was determined under what conditions Schwann cells express major histocompatibility complex class II (MHC class II) antigens, since these molecules are thought to have a key role in antigen presentation during cellular immune responses. In situ andin vitro preparations from newborn and adult rat sciatic nerves were used as a model system to examine this question. Schwann cells in dissociated cell cultures did not express immunohistochemically detectable amounts of MHC class II antigens. Teased nerve preparations from the sciatic nerves of healthy adult rats showed no detectable immunolabelling of either myelin-forming or non-myelin-forming Schwann cells. When dissociated Schwann cell cultures derived from the sciatic nerves of either neonatal or adult rats were treated with 10, 50 or 100 units of gamma Interferon, MHC class II antigens were detectable on the surface of some Schwann cells 48 h after addition of the interferon. By 72 h, 32.29 ± 3.9% of Schwann cells in the cultures from neonatal rats and 53.32 ± 5.4% of Schwann cells in cultures from adult rats, identified by the presence of intracellular S-100, were clearly MHC class II-positive, especially at doses of 50 and 100 units per ml of gamma interferon. Some, but not all, of the fibroblastic cells were very weakly MHC class Il-positive. Infection of the cultures withMycobacterium leprae did not induce MHC class II antigen expression in either Schwann cells or fibroblasts. These results suggest that one of the functional roles of Schwann cells' is the presentation of foreign antigens to T lymphocytes during nerve infection, leading to activation or augmentation of the cellular immune response. With respect toMycobacterium leprae in particular, it is therefore possible that infected Schwann cells might be capable of participating in the normal immune response toMycobacterium leprae.