Preparation of monoclonal antibody to sulfatoxygalactosylglycerolipid by in vitro immunization with a glycolipid-glass conjugate

Properties, metabolism and roles of sulfogalactosylglycerolipid in male reproduction

Sulfogalactosylglycerolipid (SGG, aka seminolipid) is selectively synthesized in high amounts in mammalian testicular germ cells (TGCs). SGG is an ordered lipid and directly involved in cell adhesion. SGG is indispensable for spermatogenesis, a process that greatly depends on interaction between Sertoli cells and TGCs. Spermatogenesis is disrupted in mice null for Cgt and Cst, encoding two enzymes essential for SGG biosynthesis. Sperm surface SGG also plays roles in fertilization. All of these results indicate the significance of SGG in male reproduction. SGG homeostasis is also important in male fertility. Approximately 50% of TGCs become apoptotic and phagocytosed by Sertoli cells. SGG in apoptotic remnants needs to be degraded by Sertoli lysosomal enzymes to the lipid backbone. Failure in this event leads to a lysosomal storage disorder and sub-functionality of Sertoli cells, including their support for TGC development, and consequently subfertility. Significantly, both biosynthesis and degradation pathways of the galactosylsulfate head group of SGG are the same as those of sulfogalactosylceramide (SGC), a structurally related sulfoglycolipid important for brain functions. If subfertility in males with gene mutations in SGG/SGC metabolism pathways manifests prior to neurological disorder, sperm SGG levels might be used as a reporting/predicting index of the neurological status.

Role of sperm sulfogalactosylglycerolipid in mouse sperm-zona pellucida binding

Sulfogalactosylglycerolipid (SGG) is the major sulfoglycolipid of mammalian male germ cells. Like other sulfoglycolipids, SGG is believed to be involved in cell-cell/extracellular matrix adhesion. Specifically, we investigated whether sperm SGG played a role in sperm-egg interaction. Initially, we produced an affinity-purified, rabbit polyclonal immunoglobulin (Ig) G antibody that specifically recognized SGG (anti-SGG). Indirect immunofluorescence using anti-SGG IgG localized SGG to the convex and concave ridges and the postacrosome of the mouse sperm head. Pretreatment of sperm with anti-SGG IgG/Fab inhibited sperm-zona pellucida (ZP) binding in vitro in a concentration-dependent manner (to a maximum of 62%). This inhibition was observed at the level of primary binding. Sperm treated with anti-SGG IgG underwent the spontaneous and ZP-induced acrosome reaction at the same rate as control sperm treated with preimmune rabbit serum IgG. Fluorescently labeled SGG liposomes were shown to associate specifically with the egg ZP, whereas fluorescently labeled liposomes of galactosylglycerolipid (SGG's parental lipid) and phosphatidylserine (negatively charged like SGG) did not. Furthermore, coincubation of SGG liposomes with sperm and isolated ZP inhibited sperm-ZP binding in a concentration-dependent manner. These results strongly suggest an involvement of sperm SGG in direct binding to the ZP.

Monoclonal antibody (Mab) markers for subpopulations of rat tracheal epithelial (RTE) cells

We sought monoclonal antibodies (Mabs) that would recognize distinct subsets of rat tracheal epithelial (RTE) cells. Mice were immunized with pronase-dissociated RTE cells and hybridomas whose supernatants immunocytochemically stained subpopulations of tracheal cells were selected. We report the immunohistochemical staining properties of the antibodies and give the results of preliminary biochemical characterization of the antigens. Four different types of antibodies were produced. Antibody RTE 1 stained most RTE cells. Three antibodies (RTE 2, 7, and 13) recognized a subpopulation of nonciliated cells, both columnar and basal cells. Antibody RTE 3 intensely labeled the surface of ciliated cells. Three antibodies reacted with granule components of secretory cells; antibodies RTE 9 and 11 reacted with mucous-type secretory cells and antibody RTE 12 stained all tracheal surface secretory cells. As described in detail, some antibodies were RTE cell specific while others also reacted with cells and secretions in other organs; the antibodies did not cross react with guinea pig or rabbit tissues. Periodate sensitivity of the antigens suggested that some antibodies recognized carbohydrate moieties while others detected peptide epitopes. In some cases, Western blotting revealed the molecular weights of the antigens, but some antigens were denatured by sodium dodecyl sulfate (SDS) and heat treatment. These antibody probes provide a useful means to immunochemically study changes in cell type distribution and/or epitope expression during development, injury, and regeneration.

Studies on the spermatogenic sulfogalactolipid binding protein SLIP 1

We have purified the testicular sulfogalactolipid binding protein SLIP 1 and shown by photoaffinity labeling that it contains an ATP binding site. Purified SLIP 1 was fluorescently labeled and shown to retain specific sulfogalactolipid binding function. This probe was used to investigate the topology of SLIP 1 binding sites on testicular germ cells. The binding pattern precisely coincided with the previously demonstrated asymmetric surface domains of sulfogalactoglycerolipid (SGG). Occasionally these SGG-containing, SLIP 1-binding cell surface domains exactly coincided with structural features on the cell surface as detected by differential interference contrast microscopy. These results demonstrate that SLIP 1/SGG interactions could provide an effective intercellular communication network between testicular germ cells within the seminiferous tubule.

Development of in vitro immunization in murine and human hybridoma technology

The development of in vitro immunization in murine and human hybridoma technology is reviewed. Special consideration is given to: technical aspects of in vitro immunization of mouse B cells; quality of antibodies produced by in vitro immunization; advantages of murine in vitro immunization; technical aspects of in vitro immunization of human B cells; and the advantages of human in vitro immunization and human monoclonal antibodies. Future developments likely to be made in this area of immunotechnology are outlined.

Sulfatide-binding proteins

Sulfatides (galactosyl ceramide-I3-sulfate) and other sulfated glycolipids are found in many tissues. The cell adhesion proteins laminin, thrombospondin, and von Willebrand factor bind specifically to sulfated glycolipids. Methods for characterizing the specificity of these interactions using surface-adsorbed glycolipids are reviewed. The three proteins do not bind to other anionic lipids, including gangliosides, phospholipids, or cholesterol 3-sulfate. Binding to sulfatides is saturable and of relatively high affinity. Relative binding avidity depends on the oligosaccharide structure of the glycolipids. Binding to sulfatides in erythrocyte membranes can account for the hemagglutinating activities of the three proteins and may play a role in the interactions of these proteins with other cell types.