Comparative determination of the asialoglycoprotein receptor by ligand and antibody binding in hepatocytes from normal and diabetic rats.

The number of cell surface and total asialoglycoprotein receptors was investigated in normal and diabetic rat hepatocytes using 2 methods: ligand and polyclonal antibody binding. An identical number of immunoreactive receptors was found in both types of cells, while the ligand binding activity of cell surface receptors was reduced by 58% in diabetic rats compared with normal ones, or by 33% for total cell receptors.

Behavior of aldehyde moieties involved in the activation of suppressor cells by sodium periodate.

The treatment of mouse spleen cells with periodate at the optimal mitogenic concentration (1 mM) induces the activation of suppressor cells of the in vitro antibody response and leads to the formation of aldehydes on the carbohydrate termini of the surface sialoglycoconjugates. These aldehyde moieties are found on the C8 (N-AN 8) and the C7 (N-AN 7) derivatives of sialic acid. Immediate borohydride reduction prevents the activation of the suppressor cells. Data from this work show that borohydride reduction must be performed within the first 6 hr to prevent the generation of suppressor cells; 18 hr after the initial periodate oxidation, borohydride treatment did not reverse the in vitro suppressive activity of periodate-treated cells. The kinetics of the disappearance of aldehydes from the cell surface were studied by using [3H]borohydride labeling and chromatographic analysis of sialic acid derivatives. About 70 to 80% of the aldehyde moieties were found to be present 6 hr after periodate oxidation. After 18 hr, 50 to 70% of the aldehyde had disappeared from the lymphocyte membrane. Oxidized sialyl residues disappear completely after 60 hr of culture. This period corresponds to the de novo synthesis of sialic acid residues on the surface of periodate-activated cells. The two classes of oxidized sialyl-glycoconjugates were found to behave in different ways. In effect, our data showed that the aldehydes remaining at 18 hr are mainly located on the gangliosides, whereas the aldehyde moieties located on high m.w. glycoproteins disappear from the cell surface between 9 and 18 hr. This would suggest that the remaining aldehydes located on gangliosides are not directly involved in the expression of suppressive activity.

Release of a cytotoxic factor by macrophages stimulated with adjuvant-active peptidoglycans.

Bacterial peptidoglycans (PG) possess various immunomodulating activities, including the ability to inhibit the growth of some experimental tumors. We report here that PG induce the release by mouse (DBA/2 and C3H/HeJ) peritoneal macrophages of a cytotoxic factor (CF) that is active on L-929 cells and a 3-methylcholanthrene-induced tumor cell line but inactive on normal fibroblasts. Only the adjuvant-active PG (extracted from Bacillus megaterium and Staphylococcus aureus) were good inducers of the CF, whereas the adjuvant inactive PG (extracted from Micrococcus lysodeikticus and Corynebacterium poinsettiae) exhibited only weak activity. The CF was released within 2 hours of contact with PG either in serum-free or serum-containing media. The CF was inhibited neither by serum nor by the protease inhibitors that have been tested. It was stable for 30 minutes at 56 degrees C but inactivated after being heated for 10 minutes at 80 degrees C. After gel filtration, a single peak of activity at 80-90 kilodaltons was found. Chromatofocusing showed that the isoelectric point of the CF was 4.8.

[Changes in the suppressive activity of splenic lymphocytes of mice induced in vitro by sodium periodate during magnesium deficiency]. / Modification de l'activitié suppressive des lymphocytes spléniques de souris, induite in vitro par le periodate de sodium, au cours de la carence magnésique.

Male DBA/2 Mice were kept on a magnesium deficient diet or a control diet. The antibody response of spleen cells, after in vitro immunization with Sheep red blood cells (SRBC) was determined comparatively in the two groups of Mice, from the 19th to the 22nd day of the diet. The effect of sodium periodate treatment on the induction of in vitro antibody suppressor cells was also studies. This treatment activated suppressor cells towards anti-SRBC response in the control group, but not in the Mg-deficient group (P less than 0.002). A greater sensitivity of periodate induced T suppressor cells to Mg deficiency is suggested by the present results.

[Production of suppressor factor(s) in the in vitro antibody response by periodate oxidized spleen cells]. / Production de facteur(s) suppresseur(s) de la réponse anticorps in vitro par les cellules spléniques oxydées par le periodate.

Sodium periodate treatment of Mouse spleen cells activated suppressor cells which act on the in vitro antibody response towards sheep erythrocytes or trinitrophenyl-polyacrylamide beads. Present study shows that suppression can be mediated by soluble factor (s) released in the cultures of periodate treated cells. Production of such suppressor factor (s) was associated to the presence of free aldehyde groups generated by periodate on the lymphocyte membrane. Control or cells successively treated by periodate and then reduced by borohydride were unable to produce suppressor factor (s). Suppressor factor (s) were stable at 56 degrees C (30 mn) and inactivated at 80 degrees C (10 mn).