Biomedical subjects

F Ramirez

Publications and source records attributed to F Ramirez.

239 records · Page 14Linked to original sources

PubMedDate not supplied

WT1-targeted immunotherapy of leukaemia.

Since malignant cells are derived from normal cells, many tumour-associated antigens are also expressed in normal tissues. For examples, WT1 is expressed at elevated levels in most leukaemias, but it is also expressed at reduced levels in normal CD34+ haematopoietic stem cells and in progenitor cells of other tissues. Antigen expression in normal tissues is likely to trigger immunological tolerance and thus blunt T cell responses. This could explain the observation that WT1 vaccination in mice frequently fails to stimulate high avidity cytotoxic T cell responses. In order to circumvent tolerance, we have isolated from HLA-A2-negative donors high avidity CTL specific for HLA-A2-presented peptide epitopes of WT1. These allorestricted CTL efficiently kill HLA-A2-positive leukaemia cells but not normal CD34+ haematopoietic stem cells. However, adoptive cellular therapy with allorestricted CTL could only be performed in leukaemia patients rendered tolerant to the infused CTL by prior allogeneic stem cell transplantation. In order to circumvent this limitation, we propose to exploit the TCR of allorestricted CTL as therapeutic tool. TCR gene transfer can be used to take advantage of the specificity of allorestricted CTL and transfer it to patient CTL, while avoiding the transfer of immunogenic alloantigens from the donor CTL to the patient.

Animals↗

PubMedDate not supplied

Internal deletion in a collagen gene in a perinatal lethal form of osteogenesis imperfecta.

Cloned probes specific for unique genes have proven to be powerful tools in defining the nature of genetic diseases such as the thalassaemias and growth hormone deficiencies. A similar approach should be useful in defining heritable diseases of type I collagen, the heterotrimer of two alpha 1(I) chains and one alpha 2(I) chain, which is the most abundant member of the collagen family of proteins. Recently, cloned cDNAs and genomic DNAs for the two polypeptide chains of the type I collagen have become available and have been used to elucidate the chromosomal location of the corresponding genes. Here, we have used several of these cloned DNAs to demonstrate the presence of an internal deletion of about 0.5 kilobases (kb) in one allele for the pro alpha 1(I) chain in a patient with osteogenesis imperfecta (OI), a group of heritable disorders which are characterized by brittle bones but which are highly heterogeneous both phenotypically and biochemically.

Animals↗

PubMedDate not supplied

Human pro alpha 1(I) collagen gene structure reveals evolutionary conservation of a pattern of introns and exons.

The collagens represent an interesting example of a structurally related but genetically distinct family of proteins. Type I, the most abundant of the vertebrate collagens, comprises two pro alpha 1(I) chains and one pro alpha 2(I) chain, each containing terminal propeptides and a central domain of 338 (Gly, X, Y) repeats. The structure of the chicken pro alpha 2(I) gene shows an intriguing relationship between exon organization and the arrangement of (Gly, X, Y) repeats (see ref. 2 for review). This has led to the suggestion that the collagens evolved from a common ancestral unit of 54 base pairs (bp). Here we present the structure of the entire human pro alpha 1(I) gene and compare this with the chicken pro alpha 2(I). The exon arrangement of the two genes is remarkably similar, although the human pro alpha 1(I) is more compact because of the shorter length of its introns. The data strongly support the notion that the type I genes have evolved from an ancestral multi-exon unit, and that once the gene was translated, a strong evolutionary pressure caused it to maintain this elaborate structure.

Amino Acid Sequence↗

PubMedDate not supplied

Use of the allogeneic TCR repertoire to enhance anti-tumor immunity.

It is well established that antigen-specific T lymphocytes can inhibit tumor growth in humans and in mice, leading to complete tumor elimination in some cases. However, in many cases T cell immunity is unable to successfully control tumor progression. Since tumors are derived from normal tissues, most antigens are shared with normal tissues, although expression levels are usually elevated in malignant cells. Nevertheless, low-level expression in normal cells can be sufficient to render autologous T cells tolerant and thus unable to mount effective immune responses against tumors. Here, we review how allogeneic T cells can be used to isolate T cells that effectively recognise and kill tumor cells, but not normal cells with low level of antigen expression. The TCR of allogeneic T cells can be introduced into patient T cells to equip them with anti-tumor specificity that may not be present in the autologous T cell repertoire.

Graft vs Host Disease↗

PubMedDate not supplied

In vitro chemosensitivity of chronic lymphocytic leukemia B-cells to multidrug regimen (CEOP) compounds using the MTT colorimetric assay.

BACKGROUND: Anthracycline-containing regimens have given controversial clinical results in CLL. Therefore, we explored the in vitro behavior of CLL B-cells after exposure to the compounds included in the most frequently used combination therapy regimen (CEOP). METHODS: A 4-day MTT colorimetric assay was used in vitro to test the effect of CEOP regimen drugs, either alone or in combination, on CLL B-cells. All drugs but mafosfamide, tested in place of cyclophosphamide, were used at concentrations corresponding to the in vivo dosage employed in the CEOP regimen. Chlorambucil was also studied since it represents the standard treatment for this disease. RESULTS: Epirubicin, prednisone and vincristine displayed a cytotoxic effect in 15, 13 and 4 out of 30 samples, respectively. Combinations of the same drugs showed a synergistic effect in 6 out of 13 assays. A cytotoxic effect of chlorambucil was detected in 2 out of 5 responders to the combination of CEOP regimen drugs, and in 3 out of 7 non responders. Mafosfamide induced a reduction in cell survival in 60-80% of the samples, depending on its concentration. CONCLUSIONS: The MTT assay is suitable for evaluating the in vitro chemosensitivity of CLL B-cells to multidrug regimen compounds. In the present study 40% of samples were resistant to CEOP regimen components in vitro. The possible role of MTT in predicting the clinical response to the CEOP regimen should still be established by prospective in vitro and in vivo studies.

Adult↗