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Monoclonal antibodies to tissue-specific cell surface antigens. I. Characterization of an antibody to a prostate tissue antigen.

Monoclonal antibodies were raised to PC-3 human prostate adenocarcinoma cells, and one hybridoma, designated F77-129, was extensively purified and used to characterize a PC-3 antigen. The F77-129 antibody also showed serological reactivity with the Du-145 prostate cancer line and with three of four breast carcinoma lines tested; it showed variable binding to a colon carcinoma line. Several other lines tested, including melanomas, fibrosarcomas, and leukemias, were completely negative. Immunoperoxidase staining of frozen surgical specimens showed binding to both normal and malignant prostate and breast tissue. Injection of radioiodinated F77-129 into tumor-bearing nude mice showed specific in vivo targeting to prostatic cancer implants. The antigen also showed surface modulation by bound antibody, suggesting possible clinical utility of this antibody in delivering immunotoxins to tumors.

Adenocarcinoma↗

Evidence for a gonad-specific receptor for H-Y antigen: binding of exogenous H-Y antigen to gonadal cells is independent of beta 2-microglobulin.

This report addresses the question whether two different types of binding exist for the reaction of H-Y antigen with the cell surface. Anti-H-Y antiserum in the presence of complement was cytotoxic only for gonadal cells expressing their own H-Y antigen, but not to ovarian cells loaded with H-Y antigen. H-Y antigen was co-redistributed with beta 2--microglobulin on newborn testicular cells, but some residual H-Y activity was found on similarly treated testis cells from 15 day old rats. After beta 2--microglobulin redistribution, testis cells maintained their binding capacity for exogenous H-Y antigen prepared from epididymal fluid or Daudi cell culture supernatants. This result suggests that exogenous H-Y antigen is bound via a gonad-specific receptor which is independent of beta 2--microglobulin and that this type of binding for H-Y antigen is different from the beta 2--m-associated expression of H-Y antigen on the cell surface.

Animals↗

Molecular changes in the membranes of mouse erythroid cells accompanying differentiation.

The development of the mouse erythroblast to a mature erythrocyte is accompanied by changes in the composition and properties of the plasma membranes of these cells. Using double fluorescence techniques, we have simultaneously determined the distribution of lectin receptors and spectrin on the membranes of these cells. The lateral mobility of the lectin receptors in the membranes decreases as differentiation proceeds, and this is accompanied by an increasing concentration of spectrin associated with the membranes. The most significant concentration of spectrin occurs, however, during the enucleation of the late erythroblast, where we observe a complete segregation of the spectrin to the incipient reticulocyte, as well as a previously observed enrichment of receptors for concanavalin A into the plasma membrane surrounding the extruding nucleus. On the basis of these and other observations, we explore the possible molecular mechanisms involved in erythroblast enucleation and the role of spectrin in the regulation of protein mobility in erythroid cell membranes.

Actins↗

Receptor for the cell binding site of discoidin I.

Discoidin I, a developmentally regulated lectin in Dictyostelium discoideum, has been implicated in cell-substratum adhesion and ordered cell migration during aggregation. This depends on the cell binding site of discoidin I, which is distinct from its carbohydrate binding site. We have isolated a receptor for the cell binding site by affinity chromatography. The receptor binds immobilized discoidin I in the presence of 0.3 M galactose and can be eluted with gly-arg-gly-asp-his-asp, a synthetic peptide the sequence of which is found in discoidin I, and which blocks cell migration into aggregates. The receptor is a developmentally regulated cell-surface glycoprotein of apparent Mr approximately 67,000. Univalent antibodies specific for this glycoprotein block aggregation.

Adhesiveness↗

Two different mechanisms for the inhibition of rosette formation in mice.

The vast majority of spleen T cells (T.sRFC) which spontaneously bind to sheep red blood cells (SRBC) in an antigen-specific fashion express the Thy-1+, CD3+, CD8+ phenotype. Inhibition of rosetting by antibodies to surface molecules occurs via distinct mechanisms according to the antibody. CD8 and CD3 molecules are located in proximity to SRBC receptors and steric hindrance is the most likely explanation for the inhibition of rosetting by antibodies to these molecules. On the other hand, anti-Thy-1 antibody bound to T.sRFC induces a dynamic process involving intracellular cAMP, and which results in the inaccessibility of SRBC receptors. Thymulin could restore normal sensitivity of T.sRFC from adult thymectomized (A.Tx) mice to all inhibitory antibodies whatever the mechanism by which they hinder rosette formation. These results reinforce the idea that thymulin may act on membrane characteristics.

Animals↗

The interaction of monoclonal antibodies directed against envelope glycoprotein E1 of Sindbis virus with virus-infected cells.

Two monoclonal antibodies specific for the Sindbis virus envelope glycoprotein E1 were evaluated for their ability to maintain long-term infection when present in the medium of virus-infected cells. One of them, previously shown to have neutralizing activity and to inhibit haemagglutination, caused suppression of both virus expression at the cell surface and prolonged intracellular virus presence. The other monoclonal antibody which lacked neutralizing activity but inhibited virus-specific haemolysis caused redistribution of viral antigens on the cell surface but only slightly prolonged cell survival. Both epitopes were located on the surface of the virus. By electron microscopy it was demonstrated that the determinant associated with haemolytic activity resided near the virus membrane while the haemagglutination inhibition antibody attached near the apex of the virus spikes.

Animals↗

Hu Ly-m5: a unique antigen physically associated with HLA molecules.

A new human cell surface antigen (Hu Ly-m5) detected by a murine monoclonal antibody (E4.3) is described. The tissue distribution of the Hu Ly-m5 antigen is similar to the HLA antigens (with which it was initially confused) but it is not present on all bone marrow cells nor the U266 myeloma, and is expressed on the HLA-negative K562 cell line. Nevertheless, the Hu Ly-m5 antigen has some affinity for HLA molecules as the two entities cocap and the Hu Ly-m5 antigen copurifies with the HLA antigens on an anti-beta 2-microglobulin immunoabsorbent column; however, the antigen complexes did not withstand the procedures used for coprecipitation. Despite their similarities, the Hu Ly-m5 and HLA antigens are distinct molecular entities--Hu Ly-m5 consists of two bands of apparent molecular weight 69 and 60 K while HLA is comprised of the 43 and 12 K bands of the HLA heavy chain and beta 2-microglobulin, respectively. The function of the Hu Ly-m5 antigen is unknown, but no involvement in the cytotoxic T-lymphocyte response to influenza virus-infected cells could be demonstrated. The two properties described (apparent molecular weight and physical association with the HLA antigens) suggests that the Hu Ly-m5 antigen may be a viral-encoded protein.

Antibodies, Monoclonal↗

Description of a mouse monoclonal anti-HLA-B27 antibody HLA-ABC-m3.

The production and characterization of a new anti-HLA-B27 monoclonal antibody HLA-ABC-m3 is described. This cytotoxic IgG2a antibody binds protein A and is able to precipitate cell surface molecules of 43,000 and 12,000 daltons corresponding to the HLA heavy chain and beta 2-microglobulin. Population testing revealed that the HLA-ABC-m3 antibody reacted with the peripheral blood lymphocytes of 47/47 individuals conventionally typed as HLA-B27+ and with 5/105 HLA-B27- individuals. These five extra reactions were with individuals expressing the cross-reactive HLA-B7 alloantigen, although the affinity of the monoclonal antibody for B27 heterozygous individuals (approx 10(9) M-1) was tenfold greater than with B7 individuals (approx 10(8) M-1). In addition, HLA-ABC-m3 reactivity segregated with HLA-B27 in two families. This monoclonal antibody should be of value in the investigation of the role of HLA-B27 in disease.

Animals↗