The neutral glycosphingolipid (GSL) globotriaosylceramide (Gb3) of the globo-series was recently defined as the CD77 antigen. This B cell-associated antigen is characterized by its specific expression on germinal center B cells. In order to study the potential relation of the CD77 antigen and other GSLs to B cell activation we have performed a comprehensive analysis of the synthesis and expression of neutral GSL in tonsillar B lymphocytes. Monoglycosylceramide (GL1) and lactosylceramide (LacCer) comprised the largest portion of GSL in tonsillar B lymphocytes as detected by HPLC analysis. GSLs of the globo-series Gb3 and globotetraosylceramide (Gb4), were found in smaller amounts. Since other GSLs, like gangliotriaosylceramide (Gg3) and gangliotetraosylceramide (Gg4), could only be detected using highly sensitive antibody reactions, we assume that these GSLs occur in B cells only in minor amounts. When tonsillar B cells were density fractionated on Percoll, the light density cells, which correspond to activated cells, contained and expressed more of both globo-GSLs than cells in the higher density fraction. When the dense fraction of tonsillar B cells was activated in vitro by anti-mu/BCGF, synthesis of GL1, LacCer, Gb3, and Gb4 was biphasic, with maxima at 12 and 84 h. Surface expression of the CD77 antigen on the denser cells was strongly induced by anti-mu/BCGF during the first 24 h of cultivation followed by a rapid decline thereafter, mimicking synthesis. PMA treatment of this cell fraction caused an even stronger expression of the CD77 antigen, which lasted over 48 h of cultivation.(ABSTRACT TRUNCATED AT 250 WORDS)

The T-cell-accessory-cell interaction in mixed lymphocyte cultures was investigated in 25 patients following autologous bone marrow transplantation (ABMT) using autologous bone marrow treated in vitro with the cyclophosphamide derivative ASTA Z 7557. In a previous study using the same group of patients, T cells failed to synthesize interleukin-2 (IL-2) and proliferate in response to CD3- and CD2- mediated stimuli even in the presence of exogenous IL-2. To investigate whether this defect in IL-2 synthesis and proliferation was caused by defective cell-to-cell interactions, we analyzed mixed lymphocyte reactions (MLR) using T cells and irradiated non-T cells. When normal T cells from 10 different healthy subjects were challenged with allogeneic normal non-T cells, IL-2 production and proliferation were observed. In contrast, when normal T cells were cultured with non-T cells derived from patients found between 20 and 330 days after ABMT, no IL-2 secretion and no proliferative responses could be seen. The addition of lymphokines such as interleukin-1 (IL-1), interleukin-3 (IL- 3), tumor necrosis factor (TNF), granulocyte-macrophage colony stimulating factor (GM-CSF), and interferon-gamma (IFN-y) did not improve the reactions. Furthermore, when patients' T cells were incubated with normal, irradiated non-T cells, defective IL-2 synthesis or proliferative response was obtained. However, when IL-2 was added to these cultures, an improvement in proliferative reactions was observed. Taken together, these new data provide additional evidence that T cells early in ontogeny possessed an intrinsic defect in IL-2 synthesis and that physical cell-to-cell contact between patients' T cells and allogeneic accessory cells induced functional responsiveness to exogeneous IL-2.

The human B lymphocyte-associated CD37 antigen (gp40-52) has been characterized by the monoclonal antibody HD28. The CD37 antigen is strongly expressed on surface immunoglobulin positive B lymphocytes and weakly on a subpopulation of T lymphocytes and myeloid cells. The total molecular mass of the antigen ranges from approximately 40 to 52 kDa in B cell-derived leukemias and malignant lymphomas as well as in normal and anti-mu/B cell growth factor-activated tonsillar B cells. The polydisperse nature of the electrophoretic pattern of the CD37 antigen was found to be due to a microheterogeneity in its carbohydrate moiety. Biochemical analysis showed that the CD37 antigen derived from B cell-lines BJAB and LICR-LON-HMy2 consists of a single chain protein core of approximately 25 kDa to which two N-linked, complex carbohydrate antennae of various length are bound. The glycosylation of the molecule comprises about 50% of the total molecular mass. The molecule does not contain O-linked carbohydrate chains. In contrast, the non-Hodgkin's lymphoma cell line, OCI.LY1, which is growth-dependent on human serum, carries a CD37 antigen with an additional carbohydrate chain resulting in a total molecular mass of approximately 40 to 64 kDa. At the electron microscopy level, this cell surface-expressed antigen was found to be associated with intracellular vesicles. The subcellular distribution of the CD37 antigen may reflect a function of this antigen both at the cell surface and in the cytoplasm. We found that, both due to its peculiar biochemical structure and its ultrastructural distribution, the CD37 antigen closely resembles the 46-kDa species of the mannose 6-phosphate receptor. The implications of this possible congruence for the function of the CD37 antigen are discussed.