Typing of murine cell-surface antigens by cellular radioimmunoassay

Solid-phase radioimmunoassay for the measurement of surface antigens expressed on intact lymphocytes

A solid-phase radioimmunoassay was developed for the measurement of lymphocyte surface antigens. The assay was performed in microplates, using cells that were initially fixed to the wells by air drying. The method was used for the measurement of Thy-1, Lyt-1,2,3, IL-2-R, H-2Kb and DR antigens on the surface of mouse thymus, spleen and bone marrow cells, mouse cell lines CTLL, EL-4 and DA-1 and human thymocytes and consisted of sequential incubations with rat or mouse monoclonal antibodies directed against the above antigens, rabbit anti-rat or goat anti-mouse IgG and 125I-protein A. The assay permits the processing of large numbers of samples, is easy to perform, reliable and highly specific.

Use of an automatic cell harvester in a cellular radioimmunoassay

An automatic cell harvester was used in the final step of a cellular radioimmunoassay to collect cell bound anti-rat IgG 125I-F(ab')2. Studies on the reliability of this collection method were performed with antibodies directed against cell surface antigens induced by the Gross murine leukemia virus and produced by immunization of W/Fu rats with the syngeneic (C58NT)D lymphoma. Glutaraldehyde-fixed as well as untreated Gross virus induced lymphoma cells could be used. Similar and specific antibody binding curves were obtained when the cells were incubated with the anti-(C58NT)D serum and anti-rat IgG 125I-F(ab')2 in the presence of 0.1% NaN3. Background levels of non-specific binding of anti-rat 125I-F(ab')2 to mouse lymphoma cells or rat thymocytes were only a few cpm above the background of the gamma-counter. This allowed detection of surface immunoglobulin positive lymphocytes among as few as 30,000 rat splenocytes. In addition, this cellular radioimmunoassay was found to be suitable for the measurement of solubilized cell surface antigen by its capacity to inhibit the binding of the specific antibodies to the target cells.

Detection of H-2Dd and H-2Kd molecules in purified Rauscher leukemia virus

Evidence is presented that an H-2 antigenic activity is associated with Rauscher murine leukemia virions grown in vitro. Purified Rauscher MuLV grown in fibroblasts of BALB/c (H-2d), C57BL/6 (H-2b) or (BALB/c X C57BL/6)F1 (H-2d/b) were used to absorb the activity of anti-Dd, anti-Kd, anti-Db or anti-Kb antisera tested against H-2-related targets by cellular radioimmunoassay. The results show that Dd and Kd activities were associated with the virions grown in H-2d or H-2d/b fibroblasts. No H-2b antigenic activity was detected in the virions grown in C57BL/6 or F1 fibroblasts. Immunoprecipitation of surface-labelled spleen cells revealed that Rauscher MuLV grown in BALB/c or F1 fibroblasts inhibited the precipitation of the 48 000 dalton peaks characteristic of the Dd and Kd molecules whereas the precipitation of H-2b molecules was not modified by Rauscher MuLV grown in the different cell lines. Class II molecules (Ia) were not detected in Rauscher virions. Comparison of the absorbing activities of intact and disrupted viruses suggests that the H-2 activity was localized at the viral surface. Taken together, these results confirm the possible non-random association of H-2 molecules to type-C viral particles whatever the nature of this association and its possible cellular or extracellular origin. However, the H-2 antigens found in the virions being a non-restricting element of anti-viral cytolytic T lymphocytes in the same system, these results give no particular support to the "altered self" hypothesis.

Cellular enzyme-linked immunospecific assay (CELISA). I. A new micromethod that detects antibodies to cell-surface antigens

A novel, indirect immunoassay capable of detecting human anti-HLA antibody bound to lymphocytes has been developed. This cellular enzyme-linked immunospecific assay (CELISA) utilizes an antiglobulin covalently linked to alkaline phosphatase to quantitate the amount of anti-HLA antibody bound to cell-surface HLA antigens. During the CELISA, V-bottom polyvinyl microplates served as the receptacle in which as little as 5 microliters of sera and as few as 25,000 lymphocytes per well were incubated. We devised a rapid and simple technique to transfer the cells from the original V-bottom plate to a flat-bottom plate before adding the enzyme substrate. Using this strategy, background noise because of the nonspecific adsorption of the different protein immunoreactants to plastic was eliminated. This strategy, the identification of an optimal cell concentration and an optimal conjugate source and dilution, enabled us to detect the anti-HLA activity in sera diluted out 250-fold more than their maximum titer as determined by the microdroplet cytotoxicity test. Since this assay is capable of sensitively and objectively quantitating antibody bound to cell-surface antigens, it may be of value in the areas of transplantation, blood banking, autoimmune disease, tumor immunology, and the study of cell-surface differentiation and viral antigens.

Analysis of DR-like molecules on a marmoset Epstein-Barr virus-induced cell line using a monomorphic anti-human HLA-DR monoclonal antibody

Mouse anti-HLA D region-related (DR) monoclonal antibodies have been found to cross-react with peripheral blood leukocytes from one primate species, the common marmoset (Callithrix jacchus). Immunoprecipitates of radioactively labeled cells extracted from a marmoset Epstein-Barr virus-induced cell line were analyzed by one- and two-dimensional gel electrophoresis and compared with the DR antigens of a human lymphoblastoid B cell line. Two chains of estimated molecular weights of 34 000 (alpha) and 28 000 (beta), similar to the human alpha and beta chains, have been observed in marmoset immunoprecipitates. Additionally, a set of spots located in the same area as the set of invariant spots found in human HLA-DR antigens is shown by two-dimensional gel electrophoresis. Thus, cross-reacting anti-human HLA-DR monoclonal antibodies could be used to analyze the expression and the structure of marmoset DR-like antigens.