Identification of complex formation between two intracellular tyrosine kinase substrates: human c-Rel and the p105 precursor of p50 NF-kappa B.

Immune complexes of the product of the c-rel protooncogene and of p105, the p50 NF-kappa B precursor, isolated from human T-lymphoblastoid cell lines are comprised of multiple proteins. Only p105 and human c-Rel (hc-Rel) are common to complexes precipitated with antiserum directed against either p105 or hc-Rel. Both proteins are inducible by phytohemagglutinin (PHA) and phorbol 12-myristate 13-acetate (PMA) and their subcellular distribution is affected by this induction.

Cell cycle regulation of histone H1 kinase activity associated with the adenoviral protein E1A.

Several cellular proteins form stable complexes with the proteins encoded by the adenovirus early region 1A (E1A) gene in extracts derived from adenovirus infected or transformed cells. Two of the cellular proteins that bind to E1A have been identified; one, a 105-kilodalton protein (pRb), is the product of the retinoblastoma gene, and the other, a 60-kilodalton protein, is a human cyclin A. Two other proteins that bind E1A have now been shown to be related to p34cdc2.

An in vitro transcription analysis of early responses of the human immunodeficiency virus type 1 long terminal repeat to different transcriptional activators.

In this report we introduce a simple, fast, and reliable method to prepare whole cell or nuclear extracts from small numbers of cells. These extracts were used to study transcriptional activation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) in vitro. Our results revealed that the time courses of activation of extracts derived from cells stimulated with the mitogenic lectin phytohemagglutinin (PHA) or with the tumor promoter phorbol 12-myristate 13-acetate (PMA) are different.

Enumeration of antigen sites on cells by flow cytometry.

We evaluated a cytofluorometric method for determining the number of antigens expressed on the cell surface of human lymphocytes. Using beads that have a known number of binding sites for mouse immunoglobulin and monoclonal antibodies specific for various antigens on human lymphocytes, we found that this system is quite reproducible, reliable and technically easy to perform. The greatest source of variation in expression of cell surface antigens is interdonor variability.

Down-modulation of MHC-I in a CD4+ T cell line, CEM-E5, after HIV-1 infection.

HIV-1 is capable of infecting many different cell types that express the CD4 molecule. In vivo and in vitro this infection is associated with profound immunologic defects. We have examined the effect of HIV-1 infection on the expression of MHC class I (MHC-I) molecules to explore the possibility that this important immune system molecule is perturbed after HIV-1 infection.

Evaluation of target cells for HIV-1-specific antibody-dependent cellular cytotoxicity assays.

The T cell line, CEM-E5, acutely and chronically infected with HIV-1, was used as a target cell in a standard 51Cr release HIV-1-specific antibody-dependent cellular cytotoxicity (ADCC) assay. CEM-E5, acutely infected with HIV-1, showed peak sensitivity to lysis in an HIV-1 specific ADCC assay on day 9 after infection. CEM-E5 clones, chronically infected with HIV-1, that productively express the virus were better ADCC targets than infected clones that do not express HIV-1.

Crown-gall tumors possess tumor-specific antigenic sites on their cell walls.

Rabbits were injected with cell walls obtained from crown-gall tumor tissue or the corresponding cell walls from normal potato tissue. The serum obtained from rabbits 53 days after they were injected with tumor cell walls contained immunoglobins that reacted with both tumor and normal cell walls as well as with the cells from the inciting strain of Agrobacterium tumefaciens. When this serum was repeatedly absorbed against normal cell walls and the cells of the inciting strain of Agrobacterium tumefaciens, only tumor-specific immunoglobins remained.