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contained between IO-75 pg ml-‘. At least three IgM MAbs, however, contained ~2 pg ml-’ and six contained ~75 pg ml-‘. Two of the three. IgM’s containing <2 pg ml” immunoglobulin were found tocluster with the negative controls. Among the IgG MAbs, the majority contained between 10-100 pg ml-’ Ig. At least five of the IgG MAbs contained >loO pg ml”; and six were <2 pg ml-l. Three of the MAbs containing <2 pg ml-’ IgG clustered with the negative controls. Many of the panel members containing >50 pg ml-’ antibody were found to give nonspeci- fit immunostaining on tissues and cell lines. Often this nonspecific immunostaining was eliminated when these MAbs were dilated. Al- though only a minority of the panel members contained very high or very low concentrations of antibody, the data highlight the inherent difficulties that may result, in part from this variable and suggest that efforts be made to normalise the Ig concentrations of panel members in future workshop panels.

Polyclonal anti-idiotypic antibodies mimicking the small cell lung carcinoma antigen cluster-5A interact with a panel of antibodies and induce specific immune response in animals Zwicky C, Stahel RA, Jaksche H, Waibel R, Lehmann HP, Loibner H. Division of Oncology. Deparrmenr of Medicine. Universiry Hospifal, CH-8091 Zurich. Br J Cancer 1991;63 Suppl 14:67-70.

Polyclonal anti-idiotypic antibodies (ab2) were generated by immu- nidng goats with the marine lgG2a monoclonal antibody SWA20 which recognises the SCLC antigen cluster-5A, a tumour-associated sialoglycoprotein. Ab2 was shown to bind specifically to antibody SWA20, but not to isotype matched control antibodies. Pre-incubation with ab2 completely inhibited target cell binding of antibody SWA20 and of four other antibodies to cluster-5A antigen, while no effect was seen with antibodies to cluster-l and cluster-w4 antigen. By these criteria the ab2 population consists of antibodies resembling in their reactivity pattern the cla.sterJA antigen. Ab2 was used for immunisa- tion of rabbits and two strains of mice.; control animals received PBS or nonspecific goat IgG. Anti-anti-idiotype sera (ab3) were analysed in a series of radioimmunoassays for reactivity with goat IgG and reactivity with ab2. After blocking the nonspecific anti-goat response, ab3 could be shown to bind specifically to ab2 idiotype. As examined by an indirect cell ELISA with lixed cells, two out of six ab3 sera showed significantly higher binding ratios to antigen-positive SW2 cells as compared to antigen negative control cells. These findings indicate that the goat anti-SWA20 idiotype antibodies functionally represent the SCLC antigen cluster-5A and therefore may have potential for modu- lating the anti-turnour response through idiotypic network interactions.

Cytotoxic activity of ricin A chain immunotoxins recognising clus- ter 1, w4 and 5A antigens associated with human small cell long cancer Wawrzynczak EJ, Derbyshire EJ, Henry RV, Parnell GD, Smith A, Waibel R, et al. Drug Targering Laboramy, Section of Medicine, /nsrirule of Cancer Research, Sum SMZ SNG. Br J Cancer 1991:63 Suppl 14:71-3.

The potential of mouse monoclonal antibodies raised against the human small cell lung cancer (SCLC) cell line SW2 to form active lmmunotoxins was evaluated using an indirect assay of immunotoxin cytotoxicity. MonoclonaJ antibodies recognising different SCLC-asso- ciated antigens, designated as cluster w4 and cluster 5A antibodies by the First International Workshop on SCLC Antigens, mediated the cytotoxic action of a screening agent made by linking ricin A chain to sheep anti-mouse IgG Fab’ fragment. In contrast, monoclonal antibod- ies belonging to cluster 1 gave no significant cytotoxic effects in conjunction with thescreeningagent. Immunotoxins made by thedirect chemical conjugation of ricin A chain to SWAll (cluster ~4) and SWA20 (cluster 5A) both exhibited selective toxic effects upon the SW2 cell line in tissue culture, inhibiting the incorporation of 3H- leucine by 50% at a concentration (ICd of approximately 3 x lo-l0 M. An immunotoxin made with SEN36 (cluster I) was much less potent with an IC,, >I x IO-* M.

Monoclonal antibodies recognising the cluster 2 antigen associated with human small cell lung cancer mediate the toxic effects of ricin A chain in ao indirect assay of immunotoxin cytotoxicity Derbyshire EJ, Wawrzynczak EJ. Drug Targeting Labmzory, Section of Medicine, Instin& of Cancer Research. Sumn SM2 SNG. Br J Cancer 1991;63 Suppl 1474-7.

Monoclonal antibodies (Mabs) submitted to the Second International Workshop on Small Cell Lang Cancer Antigens were screened for their ability to mediate the toxic effects of ricin A chain against the NCI-H69 cell line in an indirect assay of immunotoxin cytotoxicity. Cluster 1 Mabs, recognising the neural cell adhesion molecule, mediated little or no cytotoxic effect in combination with screening agent, ricin A chain linked to an antibody Fab’ fragment recognising either mouse or rat Mabs. In contrast, cluster 2 Mabs, recognising an epithelial tumour- associatedantigen,generallymediatedpotentcytotoxiceffects with the screening agent, inhibiting the incorporation of 3H-leucine by NC&H69 cells by between 90% and 99%. Measurements of Mab binding to the NCI-H69 cell line by indirect immunofluorescence and flow cytometry indicated that the cluster 2 Mabs generally bound in higher amouw than the cluster 1 Mabs suggesting that the cluster I Mabs were ineffective in the screen because they did not bind to the cells in sufficient amounts. However, Mabs recognising antigens other than cluster I bound to NCI-H69 cells in amounts similar to those of the cluster 2 Mabs yet did not mediate potent cytotoxic etiects in the indirect assay suggesting that the cluster 2 antigen may be intemalised in a fashion favouring the delivery of ricin A chain to the cytosol.

Immunotargeting of human small cell lung cancer wenografts in athymic mice using a monoclonal antibody (RNL-1) against a neuroendocrine-related antigen Mijnheere EF’. Bowman OC, Broers JLV, Klein Rot M, Vooijs GP. Rama&xs FCS. Depvrmenl ofP&ology, University Hospital, Nijmeaen. Br J Cancer 1991;63 Suppl 14:78-81.

A mouse monoclonal antibody (RNL-1) was raised against the variant small cell lung cancer (SCLC) cell line NCI-H82. Immunohis- tochemical studies on frozen sections showed that the antibody was reactive with most SCLC (15 out of 16) and lung carcinoids (six out of seven), while in general adenocarcinomas and squamous cell carcino- mas of tbe lung were negative. Immunocytochemical studies on 29 different cell lines derived from human lung turnours confirmed the newendocrine-related expression of the RNL-I defined antigenic determinant. lmmunoelectron microscopy showed that RNLI recog- noses an extracellular membrane domain. concentrated at adhesion sites between adjacent cells. The tissue distribution of the RNL-I defined antigen was mainly restricted to neural and neuroendocnne tissues. These immunohistochemical data suggest that RNL-I is directed agamst a neuroendocrine-related cell adhesion molecule. Being reactive with an epitope expressed on the surface of most neuroendocrine malignant cells, RNL-I (IgGl isotype) is a potential vehicle for targeting SCLC in viva. We evaluated the ability of radiolabelled RNL-I to local& human SCLC xenografts in nude mice as a first step in determining the m viva value for radioimmunodetection. RNL-1 was radioiodinated using the Bolton-Hunter labelling technique. Nude mice bearing NCI- H82 xenografts were injected intravenously with the radiolabelled RNL- I preparations, and animals were dissected 4,24,48,72 and 120 h post injection (p.i.) to determine the biodistribution of the radiolabel. The iodine-125 label accumulated in the tumour upto 48 h .i. (6.5% injected dose per gram of tissue [ID g-l]), while the label content of the normal tissuesdecreased with time. Tumour/non-tumourratios 72 h p.i. ranged from 47 (tumour/brain) to 3.1 (tumourflung). These data suggest that RN-1 is a promising candidate for in viva applications.

Human small-cell long-cancer cells are cytokine-resistant but NW LAK-sensitive Lagadec PF, Saraya KA, Balkwill FR. Imperial Cancer Research Fund, Lincoln’s Inn Fields, London WC2A 3PX. Int J Cancer 1991;48:31 I-7.

We have studied the effects of 8 cytokines and their combinations on the in vitro growth of IO human small-cell cancer lines (SCLC).