Terminal galactosyl residues of cell-surface glycoconjugates exposed on both human and murine immature T- and B-cells.

Exposure of terminal galactosyl residues on cell-surface molecules as detected by their ability to bind peanut lectin (PNL) is found to be characteristic for immature cortical human and murine thymic lymphocytes. While in prenatal mice PNL staining is found to be uniformly distributed among all thymic lymphocytes, in adult thymic a cortico-medullary gradient is detectable concerning the PNL-binding capacity of thymic cortical lymphocytes, a phenomenon that appears to be correlated to their maturational degree. In secondary lymphatic tissue, i.e. lymph nodes and spleen of man, mouse and rat, strongly labeled cells are found exclusively in germinal centers. Ultrastructurally, these cells could be identified as centrocytes and centroblasts. These observations suggest that exposed galactosyl moieties of cell-surface glycoconjugates are expressed by undifferentiated lymphocytes of both T- and B-cell lineage. Furthermore, it could be shown that PNL-binding properties of immature cells are not restricted to lymphatic tissue but can also be demonstrated on various embryonic cells of non-lymphatic origin in distinct developmental stages. Thus, they might have a fundamental significance in the course of maturation processes.