[Activation of human natural killer cells by receptor-bound immunoglobulin G]

Fc receptor-bound human immunoglobulin G can be detected in vitro and in vivo on CD16+ natural killer cells. Cross-linking of CD16-bound IgG via monoclonal antibody results in increased cytotoxic activity of effector cells.

The structure and light-dependent transient expression of a nuclear-encoded chloroplast protein gene from pea (Pisum sativum L.)

A nuclear gene encoding a light-induced transiently expressed protein that is localized in the chloroplast has been isolated from an EMBL3 library of pea DNA. The gene is a member of a multigene family. The sequence of the gene contains the complete reading frame of previously characterized cDNA clones and two introns in the 5' region of the protein coding sequence. Primer extension and S1 nuclease studies have defined the cap site. Two TATA boxes are found 5' to the initiating methionine codon. Only a limited homology is found between the presequence of the gene and transit sequences of other previously sequenced precursors. Isolated nuclei of pea have been labelled and the in vitro synthesized transcripts analysed. The results show that the light-dependent expression of the gene family is regulated at the level of transcription.

Molecular cloning of a pea mRNA encoding an early light induced, nuclear coded chloroplast protein

cDNA clones were isolated for a chloroplast protein, the mRNA of which is induced to maximum levels within 2-4 h after onset of illumination in five day old, etiolated pea seedlings.The cDNA library was constructed from poly(A)(+)-mRNA which was isolated from 4 h illuminated seedlings. The extremely short induction period of the early light induced protein(ELIP)-mRNA established the basis of our screening procedure. Colony hybridization experiments were performed with(32)P-labelled cDNA probes, synthesized from RNA of seedlings which had been exposed to different programs of illumination. Plasmid DNAs were isolated from colonies showing strong hybridization signals exclusively with cDNA corresponding to the 4 h-mRNA. Hybrid released translation of preselected plasmids p 17/C2 and p17/C4 revealed a peptide of Mr 24 000. After posttranslational importin vitro, the processed product of Mr 17 000 appears in the chloroplast. Using these clones, the expression of the ELIP-mRNA was investigated by DOT-hybridization. The ELIP-mRNA reaches maximum levels within 2-4 hours after onset of illumination. Our results correspond precisely to thein vivo characteristics and indicate positive identification of the sought clones.