Free Glycolipids Research Articles

Immunogenicity of cytolipin H aggregated with Acholeplasma laidlawii membrane proteins.

The list of immunologically active lipids found in membranes of normal and malignant cells is growing steadily since the isolation of cardiolipin in 1942 and of cytolipin H in 1958 (1, 2). The purified lipids usually function as haptens, failing to elicit an antibody response when injected into animals (2). Antisera to the lipid haptens have, therefore, been prepared either by injection of tissue fractions or of the purified lipids mixed with protein of a different species. Both methods are not completely satisfactory as tissue fractions may contain several serologically active lipids resulting in sera of low specificity, and the injection of the purified lipid hapten mixed with swine serum or albumin and adjuant frequently fails to elicit a good antibody response to the lipid (2). A new approach to the preparation of antibodies to lipid haptens has recently been proposed by us (3). Purified glycolipid haptens of Mycoplasma pneumoniae were bound to membrane proteins of Acholeplasma laidlawii by a reaggregation process (4) which consisted of solubilization of lipid-depleted A. laidlawii membranes and M. pneumoniae glycolipids in 20 mM sodium dodecyl sulfate (SDS) followed by dialysis of the mixed solutions against 20 mM Mg2+ . The reaggregated material elicited the production in rabbits of antibodies which fixed complement and precipitated the purified glycolipids (3, 5). Free glycolipids or their mixture with A. laidlawii membrane proteins were far less effective in evoking these antibodies (3). The main advantage in utilizing hybrid reaggregates consisting of protein and lipid derived from membranes of two different organisms lies in the ability to select the lipid and the protein components of the reaggregate and thus control the type of antibodies produced. The reaggregation process seems to involve an intimate binding of lipid to protein, presumably by the same kind of bonds responsible for their association in biological membranes.

Phospholipides et glycolipides d'une souche de Micromonospora

Summary The lipid composition of a strain of Micromonospora was examined. The total lipid extract accounted for 5 p. 100 of the dry weight of the cells and consisted of glycerides, free fatty acids, glycolipids (together 35–40 p. 100) and phospholipids (60–65 p. 100). The phospholipids were separated by column and thin layer chromatography into cardiolipinlike compounds, phosphatidylethanolamine, lysophosphatidylethanolamine, phosphatidylinositol and phosphatidylinosito-monomannoside. A very small fraction was identified as a glycolipid containing trehalose acylated by two fatty acids. The taxonomic relationship between various Actinomycetales is discussed.

Immunogenicity of Mycoplasma pneumoniae glycolipids: a novel approach to the production of antisera to membrane lipids.

The glycolipid haptens of Mycoplasma pneumoniae were bound to membrane proteins of acholeplasma laidlawii (formerly Mycoplasma laidlawii) by reaggregation. This process consisted of the solubilization of lipid-depleted A. laidlawii membranes and M. pneumoniae glycolipids in 20 mM sodium dodecyl sulfate, and dialysis of the mixed solutions against 20 mM Mg(2+). The hybrid reaggregate, collected by centrifugation, was highly immunogenic in rabbits, eliciting the production of a high titer of antibodies that fixed complement with the purified glycolipids and inhibited the metabolism of M. pneumoniae cells. The free glycolipids, or their mixture with A. laidlawii proteins, were much less effective in stimulating these antibodies. The antibodies to the hybrid reaggregate agglutinated M. pneumoniae cells and inhibited their ability to absorb erythrocytes, which indicates that at least some of the serologically-active glycolipids are exposed at the outer membrane surface. The ability to bind selected membrane lipids to membrane proteins of a serologically unrelated species provides a new tool for producing antibodies to lipid haptens.