Isolation and characterization of an isoantigenic variant from a heterozygous mouse lymphoma in culture

Immuno-selection in vivo of H-2D phenotypic variants from a metastatic clone of sarcoma cells results in cell lines of altered metastatic competence

To find out whether manipulation of H-2 expression on metastatic cells could alter their metastatic properties, we immunoselected in vivo H-2 antigen variants from a metastatic clone of the T10 sarcoma [originating in a (C57BL/6J X C3H.eB)FI mouse] and tested their metastatic capacity. The unselected metastatic cells (IE7) were previously found to express H-2Db and H-2Dk antigens, but they did not express the H-2K antigens of either parental haplotype. Transplantation of IE7 cells into C57BL/6J irradiated mice resulted in loss of H-2Dk expression and a reduction in H-2Db antigen density. Further transplantation of these cells into non-irradiated C57BL/6J mice led to a total loss of H-2 expression. The cells concomitantly lost their metastatic potency. Immunoselection of IE7 cells in C3H.eB irradiated and non-irradiated mice resulted in cells which were H-2Dk-positive but H-2Db-negative. Cells of these selected variants not only retained their metastatic potential, but in fact were far more metastatic than the unselected IE7 cells. Thus, changes in H-2 expression on tumor cells may alter their metastatic potential. In the case of T10 cells, H-2Dk expression seems to be directly involved in their metastatic capacity.

Tumor progression in metastasis: an experimental approach using lectin resistant tumor variants

A novel model of tumor progression in metastatic cancer is described which grew out of attempts to derive stable non-metastatic variants from a highly metastatic mouse tumor called MDAY-D2. The variants were obtained by selection of so-called lectin-resistant (LecR) membrane mutants using toxic concentrations of wheat germ agglutinin (WGA) as the selective agent, after mutagenesis. Cloned WGAR variants almost all appeared to be highly tumorigenic and metastatic, but displayed altered growth properties which were highly suggestive of major cellular phenotypic alterations occurring prior to metastasis. This were confirmed with the discovery that spontaneous visceral metastases always consisted of WGA-sensitive (WGAS) 'revertant' tumor cells. Such revertants also arose at the site of the subcutaneous inoculation and, with time, comprised an increasing proportion of the tumor cells at that location. The WGAS/high metastatic phenotype was stable in vitro or in vivo, implying the WGAR leads to WGAS shift had an underlying genetic basis. Thus, it appeared that the WGAR tumor cells could not metastasize, because of either an intrinsic cellular defect or a host imposed barrier, but that this block could be circumvented through a genetic change in the WGAR tumor cells which was accompanied by reversion of the WGAR phenotype. Non-tumorigenic (tum-) WGAR variants were also obtained, but in these cases the mutagenesis treatment itself appeared responsible for development of the tum- phenotype. The reduced tumorigenicity had an underlying immunological basis, a finding which could be exploited to immunotherapeutically treat established visceral metastases of poorly immunogenic tumors. Throughout these studies, emphasis was placed on the considerable potential of using tumor cell populations having various stable drug-resistant genetic markers to monitor aspects of tumorigenesis, tumor progression, and metastasis.

Gamma ray-induced loss of expression of HLA and glyoxalase I alleles in lymphoblastoid cells

Gamma rays from a cesium source were used to generate human lymphoblastoid cell line variants that had lost expression of all major histocompatibility complex antigens coded for by a single haplotype. The cell line was heterozygous at the glyoxalase I locus and had the HLA haplotypes HLA-A1, B8, DRw3, and HLA-A2, B5, DRw1. We selected with anti-HLA-B8 antiserum in a population of cells that had been irradiated with 300 R. The incidence of B8-loss variants was 4.1 X 10(-5) on day 5 after irradiation. Analysis of variants showed that expressions of HLA and GLO alleles trans to B8 were retained. However, expression of additional cis-linked HLA and GLO gene products was lost in 12 of 17 variants. Variants that had lost expression of (i) HLA-B8, (ii) HLA-B8, A1, (iii) HLA-B8, A1, DRw3, or (iv) HLA-B8, A1, DRw3 and the cis-linked glyoxalase I allele were obtained. Karyotype analysis was performed on eight variants that had lost expression of two or more cis-linked alleles. Three variants had two normal appearing no. 6 chromosomes, four variants had a deletion that included the region coding for HLA genes on the short arm of one no. 6 chromosome, and one variant had an inversion or translocation involving the short arm of one no. 6.

Separation of cells with different histocompatibility (H-2) antigens by passage through cellular immunoadsorbent columns

The anti-Ig column technique of Wigzell et al. (Scand. J. Immunol. 1972. 1:75) was adapted to the separation of mouse cells with different H-2 antigens. Fractionation was achieved by a two-step procedure: first the cells were treated with anti-H-2 sera, and thereafter passed over anti-mouse Ig columns. Antibody-coated cells were selectively retained in the anti-Ig column. The method could be applied to the separation of normal mouse lymphocytes or lymphoma cells with different H-2 antigen complexes and for the selective isolation of H-2 loss variants from a mouse carcinoma/fibroblast hybrid.

Isolation and characterization of HL-A variants in cultured human lymphoid cells

We have developed a procedure for immune selection in an established human lymphoid cell line based on HL-A, the major human histocompatibility locus. After a single brief exposure to selective conditions, HL-A2 variant clones were isolated from an HL-A2/HL-A3 heterozygous line. The variant clones occurred at a frequency of about 1 x 10(-6). The variant phenotype was stable during prolonged growth in the absence of antiserum after isolation. The variant sublines bound [unk] 1/1000 the HL-A2 antibody per cell as the parent line. Variation was specific in that expression of antigens not selected against was unimpaired. Loss of the chromosome bearing HL-A2 was excluded as the cause of variation because the variants, like the parent line, were heterozygous for phosphoglucomutase (EC 2.7.5.1) determined by structural locus PGM(3), which is linked to HL-A.

Isoantigenic variants: isolation from human diploid cells in culture

Variant human fibroblast substrains, resistant to a cytotoxic human isoantiserum, were isolated from sensitive strains by repeated exposure to isoantiserum and rabbit complement. The resistant phenotype was stable, apparently occurred at low frequency, and was associated with loss of surface isoantigens.