The functional activities of IgG and IgM anti-A and anti-B

The rate constants for association and dissociation, and the equilibrium constants, were determined for ¹²⁵I-labelled anti-A and anti-B of both IgG and IgM molecular types. The following results and conclusions were obtained:

1. The equilibrium constants were within the range 06×10⁸–13.0×10⁸ l/mole, and were of the same order for both IgG and IgM antibodies.

2. The initial rate constants for association were in the range 2.1×10⁵–4.8×10⁵ l/mole/sec, and the energy of activation (E_a) 6700–9000 cal/mole. These results indicate that the rate of association is approaching the limit set by the rate of diffusion of the reactants.

3. The initial rate constants for dissociation were 1 × 10^-4–5 × 10^-4/sec and E_a = 20,000–36,000 cal/mole. These latter values suggest that more than one bond must be broken simultaneously during dissociation.

4. Ionic strength and pH changes have only a minor effect on the constants; this indicates absence of ionic groups on A and B antigen sites.

5. The changes in enthalpy were –5400 to –21,800 cal/mole; the reactions are mainly enthalpy driven and this accounts for the fact that anti-A and anti-B agglutination titres increase as the temperature is decresed.

6. There was heterogeneity of the values of the standard change in free energy, enthalpy and entropy within each example of antibody.

7. The approximate concentrations of antibody at the end-points of the agglutination titres were: for IgG antibody, 0.2 μg/ml; for IgM antibody, 0.01 μg/ml.

     

Comparison of a modified microagglutination technique for HBsAg with the standard technique and a new RIA system.

A further modification of the standard RPHA technique (Hepatest, Wellcome Reagents) for the detection of HBsAg is described. This modification does not require a centrifugation step which is required by the other modifications that have been described previously and consequently takes a little longer to perform. It does, however, retain the advantages of increased sensitivity and decreased costs which are also features of the other modifications. A series of 939 routine clinical specimens were used to evaluate the method described and to evaluate a new RIA kit for the detection of HBsAg (Hepatube, Wellcome Reagents). Of 53 specimens found to be positive for HBsAg by RIA, 50 (94% were detected by the modified Hepatest RPHA as opposed to 47 (89%) by the standard technique.     

Inclusion of satellites in an 18/21 translocation chromosome shown by ammonical-silver staining (sat-banding) in case of partial trisomy 18.

A male infant with a partial trisomy 18 and a 46,XY, --21, t(18;21)(18qter replaced by 18q12::21 p13 replaced by 21 qter) chromosome complement is described. The translocation chromosome is of special interest because it includes the satellites of chromosome 21. This was shown by differential satellite staining with the ammoniacal-silver technique.     

Use of 125I-secretin to identify and characterize high-affinity secretin receptors on pancreatic acini

We prepared 125I-secretin and studied the kinetics, stoichiometry, and chemical specificity with which the labeled peptide binds to dispersed acini prepared from guinea pig pancreas. Iodinated secretin retained intrinsic biological activity in that it was as effective but 2.5-times less potent than native secretin in its ability to bind to pancreatic acini and to increase cellular cAMP. Scatchard analysis of binding of 125I-secretin indicated that each pancreatic acinar cell has approximately 93,000 binding sites, half of which are occupied by 11 nM iodinated secretin. Binding of 125I-secretin was rapid, reversible, saturable, specific, and temperature dependent. Binding of 125I-secretin was inhibited by secretin, vasoactive intestinal peptide, PHI, and Gila monster venom but not by glucagon, gastric inhibitory polypeptide, cholecystokinin, caerulein, gastrin, bovine pancreatic polypeptide, somatostatin, neurotensin, leucine-enkephalin, methionine-enkephalin, carbachol, bombesin, litorin, eledoisin, physalaemin, or substance P. With agonists (secretin, vasoactive intestinal peptide, PHI, or Gila monster venom), as well as antagonists (C-terminal fragments of secretin), there was a close correlation between their relative potencies for inhibiting binding of 125I-secretin and their relative potencies for increasing cAMP (agonists) or inhibiting the secretin-induced increase in cAMP (antagonists). For a given agonist, however, a 40-fold higher concentration was required for half-maximal inhibition of binding of 125I-secretin than was required to produce a half-maximal increase in cellular cAMP. Thus, maximal stimulation of cellular cAMP occurs when approximately one-third of the secretin receptors are occupied by an agonist.     

Flow of cells from polar to mural trophectoderm is polarized in the mouse blastocyst

During growth of the blastocyst there is a net flow of cells from the polar to the mural trophectoderm which is presumed to be radially symmetrical. However, such a pattern of cell movement is inconsistent with findings from a recent clonal analysis. To visualize the overall flow of cells directly, the polar trophectoderm of expanding blastocysts was labelled globally with fluorescent microspheres. Following further growth, the great majority of blastocysts that remained labelled throughout the polar trophectoderm exhibited a polarized rather than radial spread of label into the mural region. This was the case regardless of the labelling technique, whether the blastocysts were grown in utero or in vitro, or had the zona pellucida removed or left on. Intriguingly, where there were two foci of spread of label into the mural trophectoderm rather than one, these were diametrically opposite each other. In further experiments, fluorescent lineage labels were used to distinguish junctional trophectoderm cells with and without an extension onto the blastocoelic surface of the inner cell mass. The location of clones formed following further blastocyst growth provided no evidence that egress of cells from the polar trophectoderm is restricted circumferentially by the presence of junctional cells having an extension.     

Inhibition of TGF-beta modulates macrophages and vessel maturation in parallel to a lowering of interstitial fluid pressure in experimental carcinoma

A pathologically elevated interstitial fluid pressure (IFP) is a characteristic of both clinical and experimental carcinoma. The soluble TGF-beta receptor type II-murine Fc:IgG2A chimeric protein (Fc:TbetaRII) lowers IFP in the KAT-4 experimental model for anaplastic thyroid carcinoma. Analyses of messenger RNA (mRNA) expressions by Affymetrix microarrays and RNase protection assays, as well as of protein expressions identified tumor macrophages as targets for Fc:TbetaRII. Treatment with Fc:TbetaRII reduced albumin extravasation, increased coverage of alpha-smooth muscle actin-positive cells and reduced expression of NG2, a marker of activated pericytes, in KAT-4 carcinoma blood vessels. Specific inhibition of interleukin-1 (IL-1), a major cytokine produced by activated macrophages, lowered carcinoma IFP to a similar degree as Fc:TbetaRII but had no significant effect on the parameters of blood vessel maturation. Neither Fc:TbetaRII nor inhibition of IL-1 changed blood vessel density. Finally, pretreatment of KAT-4 carcinomas with Fc:TbetaRII increased the antitumor efficacy of doxorubicin. Our data emphasize a potential role of tumor macrophages in carcinoma physiology and identify these cells as potential stromal targets for treatment aimed to improve efficacy of chemotherapy.     

The 4p- syndrome—An autopsy study

The autopsy of an infant with the 4p- or Wolf-Hirschhorn syndrome revealed visceral abnormalities not previously described, i.e., agenesis of the gallbladder and spleen. The parent's chromosomes were normal.     

Complement fixing antibody responses to virus infection in children with acute lymphoblastic leukaemia.

Thirty children with acute lymphoblastic leukaemia (ALL) were studied and had a virus isolated. Only 50% produced a significant rise in complement fixing (CF) antibody titre compared to 100% of normal children. The failure to produce antibodies was unpredictable. CF antibodies are not a reliable guide to virus infections in children with ALL.