Serological and chemical specificities of twelve monoclonal anti-Lea and anti-Leb antibodies.

The serological specificities of twelve hybridomas were compared as to their chemical reactivity as determined using direct binding to synthetic carbohydrate structures. All anti-Lea cross-react with type-1-precursor structures and three different variants of anti-Lea could be defined by their binding to type-3-precursor chains, sialylated compounds and the monosaccharide D-galactose. Three major reactivity patterns were also identified among anti-Leb reagents. Anti-LebL cross-react with Lea and do not significantly bind to H-related structures. Anti-LebH,L had both anti-LebL-like activity (cross-reaction with Lea) and anti-LebH-like activity (cross-reaction with H). Finally, anti-LebH cross-reacts strongly with H compounds and do not bind to Lea. The binding pattern of anti-LebL suggests that these antibodies have lower affinity for ALeb and BLeb pentasaccharides than anti-LebH. All these specificities are not absolute, but rather are expressed as members of a quantitative progressive varying series, suggesting the existence of a whole range of antibody specificities gradually changing from Lea----Lea,b----LebL----LebH,L----LebH. The results suggest that anti-LebL will always cross-react with Lea and that anti-LebH will always cross-react with H related structures. However, under certain well-defined conditions these cross-reactions may not be apparent and antibodies might behave as specific anti-Lea or anti-Leb in certain tests.

Stimulation of [3H]thymidine uptake in mouse marrow by granulocyte-macrophage colony stimulating factor from mouse lung conditioned medium.

Stimulation of [3H]thymidine uptake in mouse marrow cells by a haematopoietic factor, granulocyte-macrophage colony stimulating factor from mouse lung conditioned medium, was used to follow the activity of the factor in the medium, and during its partial purification from the medium. The assay was performed in microtitre plates and found to be much easier and faster than conventional colony counting. The marrow cells were incubated in flat-bottomed plates in the presence of the factor for 5 days before labelling with [3H]thymidine (2 muCi/well, 5 Ci/mmole) for 6 h. Stimulation of the [3H]thymidine uptake was compared with the development of granulocyte-macrophage colonies in semisolid methylcellulose culture. The activity followed by both assays showed identical behaviour when subjected to ammonium sulphate precipitation, Sephadex gel filtration, concanavalin-A-Sepharose chromatography and polyacrylamide gel electrophoresis.

Comparison of colony stimulating activities secreted into mouse lung conditioned medium in the presence and absence of lithium chloride.

Inclusion of lithium chloride during the process of secretion of granulocyte-macrophage colony stimulating activity (CSA) into mouse lung conditioned medium resulted in an increased production of CSA. CSA produced in the presence of lithium chloride was compared to the CSA produced in its absence by means of ammonium sulfate precipitation, Sephadex G-1CO (S) chromatography, concanavalin A-Sepharose chromatography and polyacrylamide gel electrophoresis. It was found that the two activities behaved identically, indicating that lithium-induced increase in CSA does not involve a qualitative change in the molecule of the colony stimulating factor, but reflects an increased production (or release) of a CSF molecule that is similar to the one produced in its absence.