Macrophage inflammatory protein-1 alpha rapidly modulates its receptors and inhibits the anti-CD3 mAb-mediated proliferation of T lymphocytes

Macrophage inflammatory protein-1 alpha (MIP-1 alpha) is a member of the intercrine/chemokine family which consists of basic, heparin-binding, small molecular weight proteins. We have previously shown that a T cell line, CTLL-R8, carried high-affinity receptors for MIP-1 alpha and the proliferation of CTLL-R8 cells was inhibited by murine recombinant (mr) MIP-1 alpha. We extended our previous studies to murine resting splenic T lymphocytes to determine whether the inhibition of T cell proliferation is a general property of MIP-1 alpha. The resting splenic T cells carried approximately 680 high-affinity binding sites for mrMIP-1 alpha; more than 90% of the primary T cells carried MIP-1 alpha receptors. When the T cells were stimulated with immobilized anti-CD3 mAb in the presence of accessory cells, the MIP-1 alpha binding was reduced. The lowest binding was obtained 2 h after anti-CD3 mAb stimulation due to the internalization of MIP-1 alpha receptors. mrMIP-1 alpha inhibited the anti-CD3 mAb-mediated proliferation of murine splenic T lymphocytes. The maximum inhibition was obtained when mrMIP-1 alpha was added 30 min before anti-CD3 mAb stimulation. Slight inhibition of T cell proliferation was observed when mrMIP-1 alpha was added at the same time as anti-CD3 mAb stimulation. These results indicate that T lymphocytes are regulated negatively by MIP-1 alpha, which occurs when the T cells are exposed to MIP-1 alpha before activation. The negative effect of MIP-1 alpha seems to be mediated in part by the inhibition of IL-2 production, for there was a reduction in both the IL-2 mRNA levels and the IL-2 activity in supernatants from T cells preincubated with MIP-1 alpha before anti-CD3 mAb stimulation.

Macrophage inflammatory protein-1 alpha rapidly modulates its receptors and inhibits the anti-CD3 mAb-mediated proliferation of T lymphocytes

Macrophage inflammatory protein-1 alpha (MIP-1 alpha) is a member of the intercrine/chemokine family which consists of basic, heparin-binding, small molecular weight proteins. We have previously shown that a T cell line, CTLL-R8, carried high-affinity receptors for MIP-1 alpha and the proliferation of CTLL-R8 cells was inhibited by murine recombinant (mr) MIP-1 alpha. We extended our previous studies to murine resting splenic T lymphocytes to determine whether the inhibition of T cell proliferation is a general property of MIP-1 alpha. The resting splenic T cells carried approximately 680 high-affinity binding sites for mrMIP-1 alpha; more than 90% of the primary T cells carried MIP-1 alpha receptors. When the T cells were stimulated with immobilized anti-CD3 mAb in the presence of accessory cells, the MIP-1 alpha binding was reduced. The lowest binding was obtained 2 h after anti-CD3 mAb stimulation due to the internalization of MIP-1 alpha receptors. mrMIP-1 alpha inhibited the anti-CD3 mAb-mediated proliferation of murine splenic T lymphocytes. The maximum inhibition was obtained when mrMIP-1 alpha was added 30 min before anti-CD3 mAb stimulation. Slight inhibition of T cell proliferation was observed when mrMIP-1 alpha was added at the same time as anti-CD3 mAb stimulation. These results indicate that T lymphocytes are regulated negatively by MIP-1 alpha, which occurs when the T cells are exposed to MIP-1 alpha before activation. The negative effect of MIP-1 alpha seems to be mediated in part by the inhibition of IL-2 production, for there was a reduction in both the IL-2 mRNA levels and the IL-2 activity in supernatants from T cells preincubated with MIP-1 alpha before anti-CD3 mAb stimulation.

IDDM patients' sera recognize a novel 30-kD pancreatic autoantigen related to chymotrypsinogen

We have examined, by western immunoblot analysis, the sera of 16 insulin-dependent diabetes mellitus patients (IDDM) for the presence of autoantibodies against proteins extracted from islet-cell enriched preparations of normal human pancreata. A novel putative autoantigen recognized by late stage IDDM patients sera was identified, and its amino acid sequence was partially determined. Islets of Langerhans were partially purified by a modified collagenase digestion procedure, and subsequent protein extracts were fractionated by one-dimensional or two-dimensional polyacrylamide gel electrophoresis (1-D or 2-D SDS-PAGE). Immunoblot analysis revealed a 30-kD species which was recognized by 4 of 16 IDDM patients sera, but none of 16 normal sera. The 30-kD protein, appeared as a single band on 1-D SDS-PAGE, but was resolved on 2-D gel electrophoresis as several distinct protein species with different isoelectric points (pI's), ranging from 7 to 9. The amino terminal sequence of one such species was partially determined by microsequencing, and the second through the fourteenth amino acids were found to be identical to the corresponding sequence in human chymotrypsinogen. The fifteenth through the eighteenth amino acids were different from the known chymotrypsinogen sequence. This region corresponds with the site that is cleaved to activate chymotrypsinogen. Based on the size and sequence homology, this antigen appears to be related to chymotrypsinogen. We conclude that this 30-kD species may be an autoantigen in some late stage IDDM patients.

Inducible T cell antigen 4-1BB. Analysis of expression and function

4-1BB is an inducible receptor-like protein expressed in both cytolytic and Th cells. Optimal induction of 4-1BB mRNA in T cells required both PMA and ionomycin stimulation, indicating that protein kinase C activation and increases in intracellular Ca2+ were required for its expression. 4-1BB was categorized as an early activation gene since the protein synthesis inhibitor, cycloheximide, blocked the induction of 4-1BB mRNA. A rat mAb, 53A2, was generated against recombinant soluble 4-1BB and was used to characterize this molecule. 4-1BB is a 30-kDa glycoprotein and appears to exist as both a monomer and a 55-kDa dimer on the cell surface of a T cell clone. The 4-1BB protein may be post-translationally modified since its predicted backbone is 25 kDa. FACS analysis indicated that 4-1BB was inducible and expressed on the cell surface of activated splenic T cells and thymocytes. Cross-linking of 4-1BB on anti-CD3-stimulated T cells with 53A2 resulted in a dramatic enhancement of T cell proliferation. This suggests that 4-1BB may function as an accessory signaling molecule during T cell activation.

Inducible T cell antigen 4-1BB. Analysis of expression and function

4-1BB is an inducible receptor-like protein expressed in both cytolytic and Th cells. Optimal induction of 4-1BB mRNA in T cells required both PMA and ionomycin stimulation, indicating that protein kinase C activation and increases in intracellular Ca2+ were required for its expression. 4-1BB was categorized as an early activation gene since the protein synthesis inhibitor, cycloheximide, blocked the induction of 4-1BB mRNA. A rat mAb, 53A2, was generated against recombinant soluble 4-1BB and was used to characterize this molecule. 4-1BB is a 30-kDa glycoprotein and appears to exist as both a monomer and a 55-kDa dimer on the cell surface of a T cell clone. The 4-1BB protein may be post-translationally modified since its predicted backbone is 25 kDa. FACS analysis indicated that 4-1BB was inducible and expressed on the cell surface of activated splenic T cells and thymocytes. Cross-linking of 4-1BB on anti-CD3-stimulated T cells with 53A2 resulted in a dramatic enhancement of T cell proliferation. This suggests that 4-1BB may function as an accessory signaling molecule during T cell activation.

[Antifoaming agent microembolism in patients undergoing extracorporeal circulation. Its frequency in post mortem material and its pathogenic potential in vitro]

Antifoam microembolisms in patients that undergo open heart surgery, represent a risk for postoperative complications. We decided to study its frequency in an autopsy population of patients who died after heart surgery. Forty-five patients were selected and histological sections from the kidneys were studied under light microscopy, scanning electron microscopy and X-ray microanalysis. Thirty-six cases (80%) showed microemboli in the glomerular capillaries lumens. There was a positive correlation between the number of particles found and the length of the surgery. Microemboli were composed of an amorphous fraction and a particulated one composed of silicon. In vitro experimentation demonstrated that the particles are capable to induce cell lysis in a dose related manner. They also are susceptible of been phagocitated by macrophages. We conclude that bubble oxygenator are capable to induce microembolisms in a high percentage of the cases studied. Components of the microemboli are cytotoxic. Therefore microembolisms could be participating in the morbidity of patients subjects to cardiopulmonary bypass.

The dose-to-mother method to measure milk intake in infants by deuterium dilution: a validation study

A validation study of the dose-to-mother deuterium dilution method to measure breast-milk intake has been carried out on ten infants from a Nutrition Recovery Centre in Santiago, Chile. Formula milk labelled with exponentially decreasing doses of deuterium oxide represented milk from a 'pseudo mother' of these exclusively bottle-fed infants. Unlabelled formula represented milk from other sources. Deuterium levels in the infants' body water were measured on saliva samples by mass spectroscopy. The data were fitted in a two-compartment steady-state model of the mother-child system to estimate the flow of labelled water from the 'mother' to the infant and the 'mother' and infant's water elimination constants. A dose-to-child experiment was also carried out on each infant to determine the deuterium dilution space and total daily water intake. Total and labelled water flows from deuterium dilution were used to calculate total, labelled and unlabelled formula milk intakes which were compared to the same quantities measured by bottle weighing. Water elimination constants calculated from the dose-to-mother experiments underestimated by 17 per cent the initially set mother constant and overestimated by 21 per cent the infant constants calculated from the dose-to-child experiments. Rate constants, however, have little effect on the estimated water flows so that there was good agreement between values from deuterium dilution and from direct weighing. Mean (SD) total formula, labelled formula and unlabelled formula intakes were 865 (129) g/d, 417 (74) g/d and 448 (106) g/d, respectively, when measured by deuterium dilution, compared with 856 (116) g/d, 414 (71) g/d and 441 (68) g/d when measured by direct weighing. The mean per cent differences were 1.1 per cent, 0.7 per cent and 1.6 per cent and the mean absolute differences for individuals, 4.3 (1.9) per cent, 4.8 (3.1) per cent and 9.7 (6.6) per cent, respectively.

Relative role of bone and kidney in the hypercalcaemia associated with the rat Walker carcinosarcoma 256

The rat Walker carcinosarcoma 256 is an animal model for humoral hypercalcaemia of malignancy (HHM). In this model, the relative contribution of bone and kidney in the hypercalcaemia of tumour-bearing rats was investigated. Daily administration of pamidronate, a bone resorption inhibitor, for 2 days prevented the increased fasting Ca2+ excretion observed in the hypercalcaemic rats, although serum Ca2+ remained high. However, the high serum Ca2+ normalised after the acute injection of ethiofos, an inhibitor of renal Ca2+ reabsorption, which was associated with a marked increase of Ca2+ excretion. Changes in Ca2+ were accompanied by similar changes in Mg2+. The results indicate that altered renal Ca2+ handling has a key role in the hypercalcaemia associated with this HHM model.

Evidence of 1,25-dihydroxyvitamin D synthesis by the rat Walker carcinosarcoma 256

We tested the existence of 25-hydroxyvitamin D-1 alpha-hydroxylase activity in the Walker carcinosarcoma 256 implanted in rats. This tumour has been shown to induce hypercalcaemia in the host animal. We found this enzyme activity in tumour homogenates, which was in the same range as that in the kidney of tumour-bearing rats. Our results suggest that 1,25-dihydroxyvitamin D synthesized by the Walker tumour might be involved in the mechanism responsible for the hypercalcaemia in the host rat.