Differences in lifespan and rate of turnover between phytohaemagglutinin responsive cells of the bone marrow and of peripheral lymphoid organs.

Radioautographic analyses were performed on PHA stimulated cultures of in vivo labelled cells obtained from mice previously injected with 3H-TdR to selectively label either cells with a rapid renewal rate (RR) or a slow renewal rate (SR). ha responsive cells in the bone marrow (BM) were found to be virtually all RR cells, whereas both RR and SR cells from lymph nodes (LN) and spleen (Spl) were stimulated by this mitogen. However, RR cells were proportionately more responsive to PHA than SR cells in all tissues examined. Only one out of 200 BM PHA blasts belonged to the SR subclass, whereas the RR/SR ratio was approximately 1/1 for LN and 2/1 for Spl. Control experiments demonstrated that significant in vitro re-utilization of 3H-TdR from dying cells did not occur in the cultures. These results support a growing body of evidence that BM PHA responsive cells are precursor T-cells which are known to have a rapid turnover rate.     

Cellular composition of the bone marrow in the chicken. I. identification of cells

Incorporation of Fe⁵⁵ in vivo was used for verifying on radioautographs the identity of chicken bone marrow cells that are in the process of heme syntheses. Under the experimental conditions all labeled cells may be considered to be linked with erythroid differentiation. They were classified into five maturational stages according to their morphology and capacity for DNA synthesis. Granulocytes were identified by the presence of specific granules. All mononuclear cells were classified as lymphocytes which had a pachychromatic nucleus, a high nucleocytoplasmic ratio, lacked the capacity for DNA synthesis, and resembled small lymphocytes of the bursa, spleen and bone marrow that bound, in vitro, anti-chicken gamma globulins labeled with I¹²⁵. Radioautography with H³TdR was used to identify proliferating and non-proliferating members of each cell population. With the use of the morphological criteria thus established, reproducible differential counts could be performed on chicken bone marrow smears also in the absence of specific labeling. In normal, 3, 4, and 8 week old White Leghorn chicks, such counts revealed the bone marrow as a member of the lymphomyeloid complex preferentially adapted to the production and maturation of erythroid cells, while the reserve of granulocytes was found to be small compared to that of mammalian marrow. The percentage of lymphocytes appears to increase with age but, in contrast to rodent marrow, a proliferating precursor cell pool for lymphocytes could not be identified in chicken marrow up to the age of eight weeks.     

Comparison of lymphocyte populations bearing surface immunoglobulins in avian bone marrow, bursa, spleen and thymus.

Rabbit anti-chicken gamma-globulin was labeled with 125I and then incubated with cells from the bursa, thymus, spleen, and bone marrow of 4- and 8-week old birds. The same procedure was carried out on 11-week-old agammaglobulinemic chickens. Autoradiography revealed that the majority of large, medium, and small bursal lymphocytes bind the antibodies while labeled lymphocytes of each type in the spleen and thymus never exceeded 11 or 4 percent, respectively. Labeled medium and small lymphocytes in the bone marrow increased from 4.2 and 1.7%, respectively, at 4 weeks of age, to 9.5 and 8.8%, respectively, at 8 weeks of age. Labeled lymphocytes of all sizes were completely absent in all tissues of agammaglobulinemic chicks, including the marrow. Therefore, the increase in frequency of labeled lymphocytes in the bone marrow with age may be a result of recruitment of cells from the bursa of Fabricius. The majority of lymphocytes in the bone marrow do not label. Therefore, lymphocytes from the bone marrow may be T cells, subsets of B cells, or neither T or B cells.     

"Early-peak" carbon monoxide production in certain erythropoietic disorders

The "early-labeled" peak (ELP) of 14CO excretion following injection of glycine-2-14C was used to study erythropoiesis in a patient with sideroblastic anemia and in four subjects with myeloproliferative disorders. The ELP was greatly enlarged in all patients, as compared with a normal volunteer. The contour of the peaks from the hematologically abnormal subjects suggested the presence of increased erythroid heme degradation. In the patient with sideroblastic anemia, all hours of the early peak were significantly reduced after transfusion. This was interpreted to mean that even the earliest or "nonerythroid" phase of the peak is influenced by erythropoietic activity, at least under conditions of erythropoietic stress.     

Fetal hemoglobin in paroxysmal nocturnal hemoglobinuria (PNH): evidence for derivation of HbF-containing erythrocytes (F cells) from the PNH clone as well as from normal hemopoietic stem cell lines.

The cellular distribution of HbF was studied in nine patients with paroxysmal nocturnal hemoglobinuria (PNH) by measuring the level of HbF and determining the number of HbF-containing red cells (F cells) in whole blood and in the population of normal cells obtained after immune lysis of the abnormal erythrocytes. The amounts of HbF and the F cell frequencies found in the normal red cells were strikingly similar to the values seen in whole blood. The observed frequencies of F cells in normal cells best fitted those expected under the assumption that the F cells arise equally from normal hemopoietic stem cells and from the stem cells with the PNH defect. Since PNH appears to be a clonal hemopoietic stem cell disorder, this evidence argues against a derivation of F cells from distinct pluripotent stem cell lines.