Influence of cell surface galactosyl determinants on splenic localization of mouse thymocytes

Ultrastructural localization of peanut lectin binding to extravascular white blood cells in the bone marrow of embryonic chicks

Labelling by the galactose-specific lectin peanut agglutinin was studied in bone marrow of the embryonic chick at the electron-microscopic level by use of both a gold-conjugated lectin and an indirect, ferritin-conjugated, biotinylated lectin. Cell surface labelling is exclusively restricted to developing and mature heterophilic granulocytes, monocyte/macrophages, mast cells/basophils, all of which appear to develop and reside in the extravascular spaces of the bone marrow. Resident small lymphocytes, which comprise a minor portion of the cell population, are also labelled. Erythroid cells and thrombocytic cells, which develop inside venous sinusoidal vessels, display no labelling. The latter cells, like extravascular leukocytes, contain surface galactosyl residues located in subterminal positions on cell surfaces, since they are labelled by the galactose-specific Ricinus communis agglutinin-I. It is postulated that terminal galactosyl residues might be involved in interactions between the surfaces of extravascular leukocytes and extracellular matrix and/or stromal cell surfaces.

Analysis of differentiation and transformation of cells by lectins

During differentiation cells are known to change their biological behavior according to their genotype. This is thought to be accompanied by a modulation of cell surface determinants expressed on the outer cell membrane. Vice versa, cell surface molecules are suggested to mediate extracellular signals to the genome. Most of these molecules integrated in the cell membrane have been proven to be glycoconjugates. The carbohydrate moieties of these molecules can be detected by means of lectins that are characterized by their ability to react specifically with distinct terminal sugar sequences. Thus, lectins have been used as appropriate tools for studying the modulation of functionally important membrane-associated molecules during the differentiation of cells, in particular of B- and T-lymphocytes. Moreover, lectins have been proven to distinguish between differentiated cells and malignant cell clones, according to the hypothesis that transformed cells possess a glycoconjugate profile that corresponds to the stage of differentiation at which they are arrested. Since lectins, like monoclonal antibodies, make it possible to study functionally important molecules that are associated with differentiation and malignancy, they might be of value for diagnostic purposes and, moreover, for analyzing malignant transformation.

Changes in the granulocyte membrane following chemotherapy for chronic myelogenous leukaemia

Granulocytes from patients with chronic myelogenous leukaemia (CML) have been previously shown to have aberrant sialylation of membrane glycoproteins. We have examined the granulocytes from CML patients receiving intermittent chemotherapy to determine the relationship of the oligosaccharide changes to treatment. Compared to cells from non-leukaemic patients, granulocytes from untreated CML patients showed less adherence to nylon wool, decreased reactivity with peanut lectin, and decreased binding of the synthetic chemotactic peptide formyl-methionine-leucine-phenylalanine (FMLP). Granulocytes from CML patients treated with chemotherapy showed nylon wool adherence, peanut lectin reactivity and FMLP binding comparable to non-leukaemic cells. Chemotherapeutic agents may interfere with oligosaccharide synthesis with a resulting change in the composition of cell surface glycoconjugates.

Influence of protein restriction on lymphoid cell populations characterized by the binding of peanut agglutinin

Cells binding peanut agglutinin (PNA) were studied in the thymus, spleen, and mesenteric lymph nodes from mice placed in the post weaning period on protein-restricted diets containing 8% (R8%) and 4% (R4%) casein. The proportion of PNA+ thymocytes and the absolute number of total and PNA+ cells in the thymus were significantly diminished in R8% and R4% mice. Larger proportion of PNA+ thymocytes showed weaker fluorescence in R8% and R4% than in normally fed (N) animals. Recovery of PNA+ thymocytes was observed in R8% but not in R4% mice at 8 weeks. The number of total and PNA+ cells was significantly diminished although the proportion of PNA+ cells was not modified in the peripheral lymphoid organs of R8% and R4% mice. Results indicate that protein restriction preferentially affected the immature cortical PNA+ cells in the thymus whereas cell depletion in the peripheral lymphoid organs occurred at the expense of both the PNA+ and PNA- subpopulations.

Regeneration of membrane sialic acid after neuraminidase treatment of leukemic granulocytes

Granulocytes from patients with chronic myelogenous leukemia (CML) were studied for their ability to regenerate surface sialic acid following treatment with Vibrio cholera neuraminidase (VCN) in vitro. Immediately after neuraminidase treatment, CML and normal granulocytes showed similar incorporation of radioactivity after surface labelling with sodium periodate/potassium-H3-borohydride (PI/BH3(4)). CML granulocytes treated with neuraminidase then incubated for 18 h in nutrient medium showed strikingly increased PI/BH3(4) labelling, usually greater than initial pretreatment values, consistent with a rapid reappearance of sialic acid in the cell membrane. This pattern was not seen in normal granulocytes. The aberrant regeneration of sialic acid in CML granulocytes in vitro could be inhibited by addition of 3 X 10(-6) M retinoic acid, suggesting either a direct effect on membrane glycoconjugate synthesis or an association with granulocyte differentiation.

Thymus cell differentiation and in vivo T-cell migration. I. Migration of lectin-selected thymocytes

The in vivo quantitative distribution and tissue positioning of mouse thymocytes selected in vitro by Lyt phenotype and lectin binding properties were examined. Lyt 1+2- thymocytes were selected for by cytotoxic elimination; peanut agglutinin (PNA) and soybean agglutinin (SBA) binding and nonbinding thymocyte fractions were separated by an agglutinin technique. Selected cell suspensions were labelled in vitro with 51chromium (51Cr) or [3H]adenosine. Labeled washed cells were injected intravenously into syngeneic recipients which were killed at 1, 24 or 48 hr. In recipients of 51Cr-labeled cells, tissues were collected for gamma counting, and the overall percentage recovery of injected radiolabel from the various tissues was assessed. Tissues collected from recipients of [3H]adenosine-labeled cells were fixed, sectioned, and processed for autoradiography; the positioning of labeled cells within the tissues was determined. Selected Lyt 1+2-, PNA-, and SBA- sets all showed significantly enhanced entry into lymph nodes and intestinal lymphoid tissues. Entry of SBA+ cells into these tissues was comparable to that of peripheral T cells. PNA- and SBA- selected sets, but not Lyt 1+2- selected cells, also showed increased localization to the spleen and lungs, and decreased localization to the liver. By autoradiography, PNA- cells entered lymphoid tissues much more than PNA+ cells, and at 1 hr fewer PNA+ cells in spleen were associated with lymphoid follicles. At 24 and 48 hr almost all labeled cells in lymphoid tissues were positioned in T-dependent areas. These results suggest that enrichment for thymocyte subpopulations described as "mature" also enriches for cells with the ability to enter lymphoid tissue. They also suggest that interactions at other tissue sites are important in the determination of in vivo migration, and that surface carbohydrate composition is an important factor in this determination.

Selective interactions of electrolectins from eel electric organ and mouse thymus with mouse immature thymocytes

The pure electrolectin, a beta-D-galactoside binding lectin from the electric organ of the electric eel Electrophorus electricus, was found to agglutinate selectively a subpopulation of mouse thymocytes. This cell population could be separated from non-agglutinated cells by 1 g sedimentation over fetal calf serum. The agglutinated cells could be identified as immature thymocytes on the basis of the density of theta-antigen they bear on their surfaces, their mitotic activity and the absence of response to the mitogenic action of phytohemagglutinin. The immature mouse thymocytes were found to bind the endogenous mouse thymic lectin (MTL) a protein that displays the same saccharide specificity as the eel electrolectin and with which it cross-reacts immunologically. MTL is secreted by mouse thymic reticulocytes in tissue culture and its specific activity is markedly increased after depleting the thymus of its thymocytes. This finding is an indication of the possible localization of MTL in the thymic epithelium. These results are discussed in the light of our recent findings that the eel electrolectin has prophylactic and therapeutic actions on the experimental auto-immune myasthenia gravis in rabbits.

Occurrence and characterization of lympho-agglutinins in Indian plants

A survey of the occurrence of lympho-agglutinins was carried out on seeds of 150 species of wild and cultivated plants. Potent agglutinins were detected in 17 extracts by employing lymphocytes of man, guinea pig, goat and sheep in the bioassay. Except for one species each of Mimosoideae, Euphorbiaceae and Clusiaceae, all the agglutinins were found in fabaceous seeds. Two of the agglutinins, namely, Parkia biglandulosa and Erythrina arborescens, were found to be monospecific for guinea pig and human lymphocytes, respectively, while the others agglutinated lymphocytes of 2-4 different species. The agglutination inhibition tests revealed the predominance of galactose (or its derivatives) binding lectins over those specific for glucose-mannose series.