Glycolipids of murine lymphocyte subpopulations: a defect in the levels of sialidase-sensitive sialosylated asialo GM1 in beige mouse lymphocytes.

Neutral glycosphingolipids as well as some of the sialic acid containing glycolipids, or gangliosides, were quantitated from thymocytes and splenic T lymphocyte preparations from normal and natural killer-deficient mice of various ages. Previously, asialo GM1 was considered the product of acid hydrolysis of the ganglioside GM1. However, in the murine lymphoid system asialo GM1 is a normally occurring glycolipid that appears to be one of the intermediates in the biosynthesis between lactosylceramide and some recently described, terminally sialosylated gangliosides (for structures see Table I). Asialo GM1, which is a putative marker for murine natural killer cells, is unaltered in thymocytes but is found at reduced levels in 5- to 15-wk-old beige mouse splenic T cell preparations. A sialosylated derivative of asialo GM1, which is sialidase sensitive, is increased in postnatal splenic lymphocytes but then falls to below normal levels in 5- to 15-wk-old beige mice. The concentration of this ganglioside is also altered in the same manner in the thymus. Analysis of the total gangliosides of beige thymus and spleen indicates that there are several possible deletions, but it still not known whether these deletions are related to the natural killer dysfunction in these mice. These studies show that there is a defect in the synthesis or degradation of several related glycosphingolipids in beige lymphocytes, at least 1 of which contains sialic acid, but whose structure remains unknown.