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SUMMARYThe present study undertook to investigate the biological significance of human leucocyte antigen expression in hepatoceilular carcinoma and to elucidate lhc role of potential modulating agents on human leucocyte antigen expression. These studies used several hepatic tumour-derived cell lines as in vitro model systems. The cell lines included PLC/PRF/5 (Alexander cell line), Hep3B. HepG2, TONG PHC, HA22T/VGH, HA59T/VGH and Mahlavu, The cell lines K562 and Raji were used as negative and positive controls, respectively. K562, a B tymphoid-derived cell line, was shown to express negligible amounts of human leucocyte anligens, while Raji, an erythromyeloid-derived cell line, expressed both class I and class II human leucocyte anligens as well as their respective invariant chains, ^2-niicroglobulin and Ii. Using an ELISA, experiments performed on these cell lines confirmed the natural expression of class I and class II antigens by the HA22T/VGH and HA59T/VGH cell lines, whereas PLC/PRF/5 displayed class II surface antigens only. The effects of modulating agents such as interferon-gamma sodium bulyrate and clofazimine on human leucocyte antigen expression were investigated using the HA22T/VGH, HA59T/VGH and TONG PHC cell lines. These agents increased class 1 and class II human leucocyte antigen expression on HA22T/VGH and TONG PHC cells, but had no effect on the HA59T/VGH cell line. The results suggest a potential use for these agents as modulators of human leucocyte antigen expression by human heptocellular cell lines.

Summary Nuclear deoxyribonucleic acid (DNA) content of hepatocellular carcinoma (HCC) in 41 South African and 47 Japanese patients at autopsy was analysed by dual-wavelength microspectrophotometry. The DNA distribution patterns were classified as type I, II, III or IV and as low ploidy (types I, II) or high ploidy (types III, IV), according to the degree of dispersion. We found a significantly higher incidence of high ploidy in South African HCC than in Japanese HCC. Moreover, type IV was significantly more frequent among South Africans than among the Japanese. These findings demonstrate that large differences in biological characteristics and clinical behaviour of HCC between South Africa and Japan may reflect differences in DNA distribution patterns which we observed between these two races.

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