We have reported the production of human
monoclonal antibodies (mAb), by the fusion of lymph node lymphocytes from a primary
carcinoma patient with murine myeloma cells. Seven heterohybridomas showed reactivity with class III
antigens, and five hybridomas (1G12, 2D4, 4H5, 5D10 and 3B10) were reactive with
class II antigens. One of these human mAbs (1G12) was intensively studied and results are presented here. 1G12 reacted strongly and specifically with five mammary
carcinoma cell lines and showed no cross-reactivity with seven normal fibroblast cells. It continuously produced human mAbs (
IgM) at a rate of 4.5-12.5 micrograms/ml over a period of 2 years. Human
mAb 1G12 (
IgM) was purified by either a combination of
anion-exchange chromatography (ABx) and gel filtration (Superose 6) or affinity chromatography (
agarose). Immunohistological analysis of frozen tissue sections was performed with biotinylated 1G12. All mammary
carcinomas analysed (n = 26) were positive, while the connective tissue of 36 different patients was completely negative with 1G12. In normal breast, endometrium and intestine only a weak or moderate staining of the epithelial cells was observed. Normal oesophagus, small bowel, cervix, uterus, lung and skin were completely negative. Partly purified tumour
antigen recognized by 1G12 had a molecular mass of 1-2 MDa and showed strong binding with Ulex europaeus
lectin I and Bauhina purpurea
agglutinin, indicative for the glucoprotein nature of
antigens. These results show that human
mAb 1G12 may be useful for the analysis of tumour-associated
antigen of mammary
carcinoma patients. In further studies the therapeutic and diagnostic application of 1G12 should be analysed in more detail.