Specific immune responses restored by alteration in carbohydrate chains of surface molecules on antigen‐presenting cells

摘要

AbstractTwo class I major histocompatibility (MHC) mutant mouse strains, H‐2bm14and H‐2bm6, differ from the strain of origin C57BL/6 (B6, H‐2b) in one and two amino acids of the H‐2Dband H‐2Kbmolecule, respectively. The bm14 Dbmutation results in specific failure of female bm14 mice to generate a cytotoxic T lymphocyte (Tc) response to the male‐specific antigen H‐Y. The allospecific Tcresponse of CD8 B6 T cells against bm6 Kbmutant spleen cells, in contrast to that against other Kbmutants, is absolutely CD4 T helper cell dependent. Purified CD8 T cells completely fail to respond. We now report that the inability to mount these specific immune responses is restored by the use of dendritic cells (DC) as antigen‐presenting cells (APC). Comparison of MHC expression on various types of APC by cytofluorimetry and quantitative immunoprecipitation showed very high expression of class I and class II MHC molecules on DC. Strikingly, examination of class I and class II molecules by isoelectric focusing revealed qualitative differences as well. We show that the surface MHC class I molecules of DC are present in greater quantity and carry on average fewer sialic acids than the same molecules isolated from other APC types such as spleen cells, lipopolysaccharide blasts or concanavalin A blasts. That sialic acids on cell surface molecules, including MHC, may play a role in antigen presentation is suggested by our finding that removal of sialic acids, by neuraminidase, can restore specific responses to nonrespon