Biomedical subjects

P K Pettis

Publications and source records attributed to P K Pettis.

6 recordsLinked to original sources

PubMed1983

Fetal hemoglobin accumulation in vitro. Effect of adherent mononuclear cells.

In clonal cultures of erythroid burst-forming units (BFU-E) obtained from blood, the accumulation of fetal and adult hemoglobins (Hb F and Hb A) was measured by radioligand immunoassay. Inclusion of adherent mononuclear cells in the culture promoted a striking increase in the relative amount of Hb F in each of 44 experiments with 14 donors. In two-thirds of the instances, this was accounted for by a selective increase in the absolute amount of Hb F. The differential effect on Hb F and Hb A accumulation was achieved without altering the maturity of the erythroid cells, their mean hemoglobin content, or the asynchrony of the production of the two hemoglobins. Virtually all bursts produced Hb F, and the population of BFU-E as a whole, rather than a selected subset, appeared to be the target of adherent cell action. When the adherent cells were excluded from the culture input, the base-line value of Hb F was reproducible for each donor over a period of several months, and correlated with the number of in vivo circulating F cells.

Adult↗

PubMed1982

Synthesis of hemoglobin F in adult simian erythroid progenitor-derived colonies.

The simian hematopoietic system is known to respond to anemic stress with the production of erythrocytes containing large amounts of fetal hemoglobin. To determine the regulatory mechanism responsible for hemoglobin F (HbF) production in stress erythropoiesis, adult simian bone marrow cells were cultured in plasma clots in the presence or absence of erythropoietin and burst-promoting activities, and the HbF content of progenitor-derived colonies was determined by radioimmunoligand assay. Three classes of erythroid progenitors were detected: BFU-E, CFU-E, and a very mature cohort of dense highly erythropoietin-responsive cells (HERC). These classes varied in inverse proportion to their maturity with respect to their potential for HbF accumulation in the colonies to which they give rise. Both erythropoietin and burst-promoting activity stimulated HbF production, particularly in colonies derived from immature progenitors. For example, under conditions of high erythropoietin stimulation, BFU-E colonies contained 13.7-37.7% HbF, CFU-E colonies contained 2.8-13.5% HbF, and HERC colonies 0-1% HbF. These results suggest that under nonstress conditions simian erythrocytes are derived almost entirely from HERC progenitors and proerythroblasts in which gamma chain synthesis is suppressed. During stress erythropoiesis, augmented HbF accumulation could be explained by the rapid entrance into the marrow of proerythroblasts directly derived from immature progenitors. Gamma chain production in these proerythroblasts is additionally regulated by the changes in environmental erythropoietin and burst-promoting activities.

Animals↗

PubMed1981

Radio-ligand immunoassay for human hemoglobin variants.

A quantitative method is described for the individual assay of human hemoglobin variants occurring singly or in mixture. The hemoglobin to be assayed is bound to specific antibody; the immune complex is attached to protein A-containing S. aureus and removed from the mixture. The hemoglobin thus isolated is quantified by its ability to bind radiolabeled haptoglobin. The technique is accurate and distinguishes among the 4 hemoglobins tested, namely Hb A, S, C and F. It has the advantage over conventional radioimmunoassay that a single probe, radiolabeled haptoglobin, is needed for the specific assay of any hemoglobin.

Genetic Variation↗

PubMed1978

Immunologic characterization and quantification of haemoglobin A1c.

Sheep antiserum developed against the human glycohaemoglobin, Hb A1c, distinguishes this fraction from the major component Hb A0. Partial cross reactivity is observed with Hb A1a and Hb A1b, as well as with analogous glycohaemoglobins from mouse and dog haemolysates. The reactivity of the haemoglobins with this specific antiserum is abolished by the reduction of the keto group of the sugar ligand. The immunological specificity displayed provides the basis of a quantitative assay for Hb A1c, suitable for studies of clinical and experimental diabetes.

Animals↗

PubMed1976

The immunologic identification of abnormal hemoglobins.

Guinea pig antisera against human hemoglobin contain antibodies to multiple antigenic determinants. Hemoglobin variants having single amino acid substitutions affecting these determinants are recognized as antigenically deficient in a radioimmunoassay system. The multivalent antisera may be made more selective by appropriate absorption with hemoglobin variants. Three such antisera containing antibodies specific, respectively, for the beta-chain of Hb A, Hb S, and Hb C are described. They can differentiate among the hemoglobins of individuals who possess these variants alone or in any paired combination. Their discriminating ability is not hindered by the presence of 1,000-fold concentrations of Hb F and may therefore be extended to the early prenatal diagnosis of sickling disorders. The antisera described also detect several other variants of Hb A. The approximate location of the substitution in variants so detected can be determined by a complementation test. This is based on the finding that two antigenically deficient hemoglobins will complement each other in mixture provided their amino acid substitutions involve different determinants.

Fetal Blood↗

PubMed1975

The modification of hemoglobin-antihemoglobin reaction by haptoglobin.

In radioimmunoassay and double diffusion experiments, the reaction between hemoglobin (Hb) and antihemoglobin antibody is markedly affected by the presence of haptoglobin (Hp). Binding with haptoglobin exposes "neoantigenic" determinants in hemoglobin, probably as a result of conformational changes exposing previously inaccessible structures. Some of these are shared by both Hb A and Hb F an may be located on alpha-chains. The exposure of these determinants requires the binding of hemoglobin by haptoglobins of the phenotype Hp 2-2 or Hp 2-1. The phenotype Hp 1-1 and guinea pig haptoglobin have no discernible effect in this context. It thus appears that the conformational change induced in hemoglobin by the "polymeric" forms of haptoglobin differ from those, if any, caused by the "monomeric" forms such as Hp 1-1. Most antisera raised against free hemoglobin contain some antibodies specific for these hidden determinants which may have become exposed during the processing of the immunizing antigen. These findings have significant implication in the interpretation of radioimmunoassay data.

Animals↗