Time course study of H-2 and other antigen expression by hybrids of a myeloma cell line with inflammatory macrophages

Mouse and human CD14 (myeloid cell-specific leucine-rich glycoprotein) primary structure deduced from cDNA clones

cDNA clones complementary to MS7-4 (Setoguchi et al. (1988) Somat. Cell Mol. Genet. 14, 427-438) from a mouse macrophage cDNA library were separated. Sequence analysis of these clones demonstrated that the longest cDNA clone, MS7X, had a 1366 bp insert and high homology with that of the human CD14 gene (Ferrero and Goyert (1988) Nucleic Acids Res. 16, 4173). Using the MS7X cDNA probe, cDNA clones were separated from cDNA libraries constructed from a human macrophage cell line and macrophages. The total cDNA sequence was 1364 bp in length, with an open reading frame of 1125 nucleotides matching that of the human CD14 gene except for one nucleotide difference. The amino-acid sequence (mouse CD14), deduced from the nucleotide sequence of the MS7X insert consisted of 351 amino-acid residues with a high leucine content (17.66%) and five putative N-glycosylation sites, and in vitro translation predicted a protein of molecular mass of 37.5 kDa. Human CD14 had 356 amino-acid residues, with high leucine content (15.5%), and contained four putative N-glycosylation sites. Mouse CD14 showed 13 building blocks, of which internal nine blocks have a conserved leucine motif and significant homology with human leucine-rich alpha 2-glycoprotein.

Molecular analysis of expression of parental cell properties in hybrids between monocytes and a myeloma cell line

Interspecific hybrid cell lines (HINS lines) between human monocytes and a mouse (H-2d) myeloma cell line, NS1, initially showed myeloma properties, but later expressed macrophage properties, while losing myeloma cell characteristics and undergoing a marked reduction in the number of chromosomes. The aged HINS cells showed mouse but not human phenotypes. Molecular genetic analysis demonstrated loss of BLUR8 genes, expression of mouse macrophage specific genes, and enhanced transcription of H-2d and mouse beta 2-microglobulin genes in the aged cells, confirming that the hybrids' macrophage properties were attributable to NS1 genes. Transcription of kappa light chain genes was not detectable in aged HINS cells, although the genes were retained. Since some rearrangements of the genes were suggested and cycloheximide treatment induced no transcription of the genes, cis mechanisms might be involved in the loss of expression of the genes.

Expression of macrophage functions in hybrids of a myeloma cell line with inflammatory macrophages: evidence for negative control mechanisms in the expression of macrophage functions

Mouse inflammatory macrophages from C57BL/6N mice were fused with BALB/c mouse-derived myeloma cells (the CANS series). The hybrids in the early period after cell fusion (8 weeks) showed no macrophage functions (chemotaxis, EA and EAC rosette-forming abilities, phagocytosis or lysozyme production). EA rosette-forming ability was observed when these hybrids were treated with trypsin, whereas other macrophage functions were not. After prolonged culture, the hybrids (12 clones of 13 randomly selected) showed all the macrophage functions along with chromosome loss. Myeloma cell functions (kappa light chain production) were found in the young hybrids soon after cell fusion but were absent in the aged hybrids. These results indicated that reexpression of macrophage properties, except for EA rosette-forming abilities, takes place after the loss of chromosomes or genes repressing the expression of macrophage functions.