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C Gravekamp

Publications and source records attributed to C Gravekamp.

26 records · Page 2Linked to original sources
PubMed1989

[Weil's disease, milker's fever and other leptospiroses, 1981-1987].

In The Netherlands, human leptospirosis is mainly caused by the serovars icterohaemorrhagiae and copenhageni, both of which belong to the Icterohaemorrhagiae group and originate from rats, serovars hardjo from cattle and grippotyphosa from voles. In 1981-1987, 175 cases of leptospirosis were registered. In 17 of these cases the infection was acquired outside The Netherlands. Infections caused by serovars from the Icterohaemorrhagiae group were mainly observed in the province of Zuid-Holland, hardjo infections in the province of Friesland. The number of hardjo infections increased. Hardjo also causes problems in cattle. Infections caused by serovars icterohaemorrhagiae and copenhageni were mainly associated with exposure to inland surface waters in relation with recreational or professional activities or accidents. Hardjo infections were characteristically associated with dairy farming. The incidences of all types of leptospirosis were highest in late summer and early autumn.

Agricultural Workers' Diseases↗
PubMed1989

Detection of leptospires in urine by polymerase chain reaction.

Primers for polymerase chain reaction (PCR) were synthesized from clones derived from a Leptospira hardjo (type hardjobovis) library. One pair of synthetic oligonucleotide primers was selected for further analysis. Under experimental conditions an amplification was obtained with DNA of Leptospira interrogans of some serovars belonging to serogroup sejroe. However, very little or no amplification was observed with DNA from other serovars of this group. No amplification was observed with DNA from other serogroups, other bacteria, or eucaryotic organisms. Cattle urine, seeded with hardjobovis, was processed in several ways and subsequently subjected to PCR. Boiling of the samples or treatment with detergents appeared to be most effective. Urine samples containing fewer than 10 leptospires gave a positive result in the PCR assay. Twenty urine samples obtained from a slaughterhouse or farm cows were investigated using the PCR assay, culture isolation, dot and quick blot hybridization, and serological tests. This comparative study suggests that amplification by PCR may be a valuable method for the detection of leptospires in cattle urine.

Animals↗
PubMed1988

OK-432 and IL-2-augmented cytotoxicity of human natural killer cells and cytotoxic T lymphocytes at the clonal level.

The biological response modifiers OK-432 and interleukin-2 (IL-2) were found to enhance the lytic capacity of cloned CD3- natural killer (NK) cells and CD3+ T cells. With respect to NK cells, only those clones with a high proliferative capacity and cultured without phytohaemagglutinin (PHA) responded with enhanced lytic capacity to OK-432. OK-432, but not IL-2, was found to augment the antibody-dependent cellular cytotoxicity of cloned NK cells. With T-cell clones, OK-432 augmented the cellular cytotoxicity of CD3+8+ but not that of CD3+4+ cytotoxic T lymphocytes, while IL-2 augmented the cytotoxicity of both types of clone. Taken together, these results indicate that OK-432-augmented lytic capacity is not restricted to NK cells and its pathway of action may be independent of IL-2.

Antigens, Differentiation↗
PubMed1987

Efforts to produce human cytotoxic T-cell hybridomas by electrofusion and PEG fusion.

Cytotoxic human T cells from different sources were fused with different types of human T-lymphoma cells and mouse B-myeloma cells using variations of the polyethylene glycol (PEG) method and electrofusion. Both techniques yielded proliferating hybridomas. The frequency of wells with proliferating hybridomas depended on the tumor fusion partner used; the best results were obtained with HSB-1, whereas fusions with JURKAT-1 and HPB-1 did not yield any hybridomas. For one tumor cell line (HSB-1), considerably more hybridomas were obtained with electrofusion than with the PEG fusion (with or without heat shock). There was no consistent relationship between the presence or absence of cytotoxic activity of the T lymphocytes against the tumor fusion partner and the yield of hybridomas. In human-human as well as in human-mouse hybridomas most of the lymphocyte derived chromosomes were lost. Four of the more than 600 hybridomas tested showed transient cytotoxic activity, but in none of them this function could be immortalized. Two of the hybridomas obtained with CEM-1 as tumor fusion partner expressed low levels of lymphocyte-derived CD3 antigens. Two hybridomas obtained with HSB-1 were highly invasive in vitro in rat hepatocyte cultures, whereas HSB-1 tumor cells were not.

Animals↗
PubMed1987

c-myc gene expression and interleukin-2 receptor levels in cloned human CD2+,CD3+ and CD2+,CD3- lymphocytes.

The levels of c-myc mRNA and interleukin-2 receptors (IL-2 Rec) were studied in human peripheral blood lymphocytes (PBL); mature CD2+,CD3+ T cell clones and CD2+,CD3- natural killer (NK) cell clones, and CD2+,CD3+ and CD2-,CD3- T lymphoma cell lines. A transient induction of the expression of c-myc and IL-2 Rec was observed in PBL after activation with phytohemagglutinin (PHA). Expression of c-myc and IL-2 Rec was also found in the CD2+,CD3+ and CD2+,CD3- clones. The CD2+,CD3+ showed higher levels of c-myc mRNA and IL-2 Rec than the CD2+,CD3- clones. In three T lymphoma cell lines constitutively high levels of c-myc mRNA but no IL-2 Rec were found. Only in JURKAT (CD2+,CD3+), c-myc mRNA levels could be further enhanced by PHA. These results suggest that in the presence of PHA, expression of c-myc and IL-2 Rec is induced via the CD3 receptor, and in the absence of PHA and/or the CD3 receptor alternative routes of induction are involved.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1986

Interferon-beta and recombinant IL 2 can both enhance, but by different pathways, the nonspecific cytolytic potential of T3- natural killer cell-derived clones rather than that of T3+ clones.

We studied the enhancement of cytolytic activity of T3- natural killer cell-derived clones, of T3+ T cell activated killer (AK) clones, and of fresh peripheral blood lymphocytes (PBL) by various crude and recombinant interferon (r-IFN) as well as IL 2 preparations. It was found that IFN-beta had the highest cytotoxicity inducing potency as compared to crude or r-IFN-alpha or -gamma preparations. This enhancement was blocked by anti-IFN-beta antibodies but not by anti-IFN-gamma antibodies. IL 2 also strongly enhances cytolytic activity in cloned T3- killer cells that express the IL 2 receptors as determined with the anti-Tac monoclonal antibody (MAb) at concentrations of IL 2 (25 U/ml) which induced one-half of the maximal proliferation capacity in human T cells and murine CTLL cells. For enhancement of cytolytic activity in fresh NK cells, a much higher concentration of IL 2 is required. In addition, the enhancement of cytolytic activity by r-IL 2 but not that by IFN-beta can be reduced by anti-Tac MAb, suggesting that the IL 2 receptor is involved in the enhancement by IL 2, but not by IFN. Both IFN-beta and IL 2 were able to enhance (over threefold) the cytolytic activity of T3- cloned killer cells against a variety of tumor target cell types. Another remarkable observation was that K562 cells, the most commonly used target cell for determining NK cell cytolytic activity, are not the most suitable targets to assess enhancement of nonspecific lytic activity as compared to Daudi or lung tumor-derived cell lines. No enhancement of anti-body-dependent cellular cytotoxicity was observed. Finally, the effects of these biological response modifiers were much more pronounced on "fresh" and cloned T3- natural killer cell-derived than on T3+-activated killer mature T cell-derived clones.

Adjuvants, Immunologic↗