Chapter 30 Characterisation of small cell carcinoma surface membrane antigens by indirect immunofluorescence. Solid phase radioimmunoassay and immunoblotting

Abstract

<h2>Abstract</h2> Five antibodies to surface membrane antigens of small cell lung carcinoma (SCLC), were selected by indirect immunofluorescence (IF). Their characteristics were compared to antibody LAM8. Antibody reactivity on a panel of lung tumour cell lines was determined by IF and by indirect solid phase radioimmunoassays (RIA). Biochemical characterisation of the antigens was done by RIA and immunoblotting. By IF antibodies SWA4, SWA20, SWA23, and LAM8 reacted selectively with 4/8 SCLC cell lines. By RIA this selectivity was lost for antibodies SWA4 and SWA23. Antibodies SWA21 and SWA22 reacted with all SCLC, weakly with one non-SCLC cell line and also stained leukocytes. RIA and immunoblotting experiments suggested antigens recognised by antibodies SWA4, SWA23 are identical to sGP90-135 identified by antibody LAM8 and suggest similarities of the antigens recognised by antibodies SWA21 and SWA22. In contrast, antibody SWA20 appeared to recognise a different membrane antigen. These results demonstrate that antibodies which recognise the same membrane antigen can differ considerably in their pattern of reactivity with cell lines depending on the method employed, and that the same pattern of cell line reactivity, even when examined over a large number of cell lines by different methods, does not necessarily establish the similarities of antigens.