Agglutination by lectins of liposomes prepared from total lipids of erythrocytes

Nature of the receptor sites for galactosyl-specific lectins on human lymphocytes

The nature of the receptors for four lectins specific for D-galactosyl residues was examined in human lymphocytes. The cells were fixed with formaldehyde to avoid subsequent cell lysis, treated with pronase, sialidase and organic solvents, and the binding of the lectins to the treated cells measured. The results show that the bulk of the receptors for peanut agglutinin (PNA) and ricin (RCA 60) are glycoproteins, whereas those for Ricinus communis agglutinin (RCA 120) and soybean agglutinin (SBA) are distributed nearly equally between membrane glycoproteins and glycolipids.

A latex agglutination test for lectin binding

Blood group A + H substance purified from hog gastric mucin was fixed to polystyrene particles by physical absorption to produce a lectin-agglutinable latex. Agglutination of this latex by soybean agglutinin, concanavalin A, and wheat germ agglutinin is specifically inhibited by the respective monosaccharide haptens and is not affected by known noninhibitory sugars. The sensitivity of the assay, a function of particle loading and latex concentration, approaches that of the hemagglutination test. NaCl, NaHCO3, NH4CO3, NH4-acetate, and Tris-HCl up to a concentration of 1 M do not interfere with the test. The latex suspension is stable for several months and can be stored in freeze-dried form.

Lectin-mediated agglutination of liposomes containing glycophorin. Effect of acyl chain length

Glycophorin from human erythrocytes has been incorporated into liposomes of dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC). The thermal properties of unsonicated liposomes with glycophorin/lipid molar ratios up to 4.10(-3) have been studied by differential scanning calorimetry and the numbers of lipids withdrawn from participation in the gel-to-lamellar phase transition were found to be 42 +/- 22 (DMPC), 197 +/- 28 (DPPC) and 240 +/- 64 (DSPC). The initial rates of agglutination of sonicated liposomes with glycophorin/lipid molar ratios up to 4.10(-3) by wheat germ agglutinin in the concentration range 0-7 microM have been measured over a range of temperature. Below the gel-to-lamellar phase transition (Tc) the rates of agglutination increase with acyl chain length in the sequence DMPC less than DPPC less than DSPC. Agglutination is found to be second order in liposome concentration and is completely reversed on saturation of the wheat germ agglutinin-binding sites by N-acetylglucosamine. Agglutination rates decrease with increasing temperature below Tc and are largely independent of temperature above Tc. The results are discussed in relation to the clustering of glycophorin in the phospholipid bilayers and its effect on binding and subsequent interliposomal bridge formation by wheat germ agglutinin.

Bilayer lipid membranes (BLM) study of antigen-antibody interactions

Previous work of del Castillo and co-workers has shown that bilayer lipid membranes (BLM) can be used as transducers for detection of antigen-antibody reactions. The present experiments extend the previous work by incorporating complement into the BLM system. The results indicate that the antigen-antibody complex or the complement has no ability to affect the BLM system separately, but when carefully combined they will destabilize the BLM as a tool for investigating immunological reactions is suggested.