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Biomedical subjects

G C Astaldi

Publications and source records attributed to G C Astaldi.

At least 19 recordsLinked to original sources
PubMed1982

Detection of HLA antigens on blood platelets and lymphocytes by means of monoclonal antibodies in an ELISA technique.

The expression of HLA-A and -B antigens on peripheral blood lymphocytes and blood platelets was measured using monoclonal antibodies in a semi-quantitative ELISA technique. Reactively of monoclonal anti-HLA-A2 and anti-HLA-B7, with lymphocytes as well as platelets, was in agreement with the presence of these antigens as detected by conventional HLA typing of lymphocytes. When the actual amount of HLA antigens was measured, a gene-dose effect was seen: cells from HLA-B7-homozygous individuals bound more monoclonal anti-HLA-B7 antibodies compared to their HLA-B7-heterozygous siblings. At the same time, cells of different donors showed only very small differences in binding of monoclonal antibody against an HLA-"backbone" determinant. Relative to total HLA-A, -B and -C expression, the amounts of HLA-A2 on lymphocytes and platelets were similar. On the other hand, the expression of HLA-B7 on platelets was diminished compared to that on peripheral blood lymphocytes.

Antibodies, Monoclonal↗
PubMed1982

Increase of hybridoma formation by human lymphocytes after stimulation in vitro; effect of antigen, endothelial cells, and PWM.

Peripheral blood lymphocytes from antibody-producing Rh- donors were fused with mouse myeloma cells, and the hybrids were screened for anti-Rh antibody production. Although the resulting hybrids were not stable in long-term culture, they provided a useful test system for an investigation of ways to stimulate human lymphocytes in vitro before fusion in order to maximize the recovery of hybrids producing antibodies with a desired specificity. Although 6-day culture with PWM or with antigen (Rh+ erythrocytes) increased slightly the yield of desired hybrids, exposure of the PBL to antigen in the presence of human endothelial cells was dramatically more effective. This effect was not produced with endothelial cell culture supernatants (HECS) that had been shown previously to enhance hybridoma growth. Culture of PBL before fusion with both PWM and antigen also improved the proportion of active hybridomas, and incubation with antigen plus endothelial cells plus PWM resulted in a very high number of hybridomas, with a very high proportion producing antibody to the immunizing antigen. There are several alternatives to explain the mechanisms involved, but in any case, the technique should be particularly useful when the possibility of fusion of human PBL with a human myeloma line becomes more widely available.

Adult↗
PubMed1981

Human endothelial culture supernatant (HECS): evidence for a growth-promoting factor binding to hybridoma and myeloma cells.

Human endothelial culture supernatant (HECS) contains a factor(s) that enhances the proliferation of hybridoma cells as we reported previously. In the present paper, we found that, in comparison with endothelial cells, their supernatant exerts a much stronger growth-promoting effect on hybridoma cells, which can also be detected earlier. In a confluent culture of endothelial cells, detectable amounts of this factor(s) are produced after 2 hr of incubation, and the production is linear in time for 3 days. The enhancing effect of HECS on the proliferation of hybridoma cells appears to be independent of the concentration of cells in the culture. The activity of HECS is adsorbed to hybridoma or myeloma cells, but not to thymocytes. HECS acts on hybridoma cells by delivering a growth-promoting signal that induces the hybridoma cells to proliferate.

Adsorption↗
PubMed1980

Subpopulations of T lymphocytes from human blood differing in density and stage of maturation.

Previous investigations have shown that peripheral lymphocytes with a low specific gravity are much more active than are heavy lymphocytes in the proliferative response towards mitogens, antigens and allogeneic lymphocytes. We have now studied the biological significance of this difference in human peripheral T lymphocytes with two independent parameters generally regarded as maturation criteria. Heavy human T lymphocytes contain about one-third of the amount of cyclic AMP found in light T cells, but the increase in cyclic AMP produced by isoproterenol or prostaglandin E1 is much higher in the heavy T cells. The lactate dehydrogenase isoenzyme pattern of heavy human T lymphocytes is intermediate between that of human thymocytes and light T lymphocytes, the latter showing the most mature pattern. A high correlation was found between these two parameters, the cell density and the reactivity towards phytohemagglutinin. We conclude that human peripheral T lymphocytes are heterogeneous in maturation level: heavy, nonreactive T lymphocytes are less mature than light T lymphocytes.

Cell Differentiation↗
PubMed1980

Immunoperoxidase procedures to detect monoclonal antibodies against cell surface antigens. Quantitation of binding and staining of individual cells.

An immunoperoxidase method has been developed which allows accurate and sensitive quantitation of the binding of monoclonal antibodies to cell surface antigens. Monolayers of fixed cells were prepared in wells of Terasaki micro-test plates and monoclonal antibodies bound to cell surface antigens were identified by the unlabeled antibody-enzyme method of Sternberger (1974). The cell-bound peroxidase could either be quantified per well or visualized on individual cells by the use of appropriate substrates for peroxidase. Experimental procedures are described in detail and results obtained with several monoclonal antibodies with specificity for different target cells are shown. Limitations and applications of the technique are discussed.

Animals↗
PubMed1980

Influence of adult thymectomy on immunocompetence in patients with myasthenia gravis.

The influence of adult thymectomy on several parameters of immunocompetence in patients with myasthenia gravis (MG) was investigated. Since incomplete thymectomy may lead to the presence of thymic remnants, we determined the activity of a thymus-dependent factor in the sera of the MG patients. As measured by several parameters, MG patients showed a normal immunocompetence compared with healthy controls, except in the response to DNCB sensitization in vivo. When tested at least 5 years after thymectomy, MG patients were found to have decreased response to mitogens, and a decreased cytotoxic T cell response in cell-mediated lympholysis. The response to challenge with DNCB in vivo was decreased both in thymectomized and nonthymectomized MG patients. No difference was found in a) the percentage of circulating T, B, non-B/non-T cells; b) the response to allogeneic cells (MLR); c) the antibody-dependent lymphocytotoxicity; d) the production of immunoglobulins in vitro by pokeweed mitogen-stimulated cells; and e) the anamnestic response to antigens in vitro. We conclude that adult thymectomy results in a decrease in the function of some subpopulations of lymphocytes.

Adult↗
PubMed1980

Human endothelial culture supernatant (HECS): a growth factor for hybridomas.

Human endothelial culture supernatant (HECS) had strong growth-promotion activity for hybridoma cells: the yield of hybridomas after fusion was increased at least 2-fold over that in the presence of feeder cells, such as mouse macrophages and spleen cells. Moreover, HECS could substitute for feeder cells when hybridomas were cultured at the single-cell level, and strongly enhanced the proliferation of hybrid cells. furthermore, the presence of human endothelial cells prolonged the stability of human-mouse hybridomas, producing human immunoglobulin, hybrids known to survive poorly during culture in vitro.

Animals↗
PubMed1979

Early events in thymocyte activation. II. Changes in nonhistone chromatin proteins induced by a thymus-dependent human serum factor.

Previously, it has been shown that a human thymus-dependent serum factor (SF), isolated from peripheral blood and acting on precursors of mature T lymphocytes, induces an increase in the synthesis of cyclic AMP and proteins in thymocytes. We have now investigated the action of SF on the incorporation of 3H-leucine and 32P-orthophosphate into nuclear proteins of thymocytes after 15 to 240 min of culture. SF induced a rapid increase in the synthesis and phosphorylation of nuclear proteins, especially in the phosphorylated nonhistone chromatin proteins (P-NHCP). Electrophoretic patterns in polyacrylamide gels of the P-NHCP fractions, extracted from the chromatin of the stimulated cells, showed that proteins with m.w. higher than 50 x 10(3) were synthesized to a larger extent as compared with unstimulated cells. These data suggest that SF acts specifically on the synthesis of P-NHCP and may in this way control DNA-template activity.

Chromosomal Proteins, Non-Histone↗
PubMed1978

Lymphoid cell surface markers in acute lymphocytic leukaemia.

Peripheral blood lymphoid cells of 29 patients with acute lymphocytic leukaemia (ALL) at onset were studied for characterization of B and T membrane markers and phytohaemagglutinin responsiveness. 24 cases (83%) were classified as "null" cell ALL and 5 (17%) as T-cell ALL. No relationship could be found between cytological presentation and immunological classification. Moreover, no correlation has been demonstrated between clinical-immunological parameters and prognosis, indicating that in our series of patients, assessment of cell size and surface markers were not a reliable predictor of prognosis.

Antineoplastic Agents↗
PubMed1978

Experiences with thymosin in primary immunodeficiency disease.

Thymosin has no effect in vitro on cyclic AMP levels in thymocytes. However, when thymosin was injected into patients lacking "serum factor" (SF) activity, it induced the appearance of SF or SF-like activity and the disappearance of target cells for SF among the peripheral blood lymphocytes of the treated patients. On the other hand, when thymosin was injected into one patient with normal SF activity, it induced a marked decrease of SF activity and the appearance of target cells for SF among the peripheral blood lymphocytes of this particular patient.

Animals↗