Morphology and nucleoside incorporation of human neonatal lymphocytes

Low responsiveness of human neonatal lymphocytes to a B-cell mitogen, Staphylococcus aureus Cowan I (SpA CoI)

Responses of neonatal and adult lymphocytes to various mitogens were studied. Lymphocytes from umbilical cord blood (UCB) responded well to both phytohemagglutinin and concanavalin A, and also to pokeweed mitogen and Staphylococcus aureus Protein A. The responses of UCB lymphocytes to these mitogens were not significantly lower than those of adult peripheral blood lymphocytes (PBL). In contrast, UCB lymphocytes showed only a minimal response to killed Staphylococcus aureus Cowan I (SpA CoI), a potent B-cell mitogen for human PBL, although the proportion of B cells in UCB was not less than that in PBL. The low level of response of lymphocytes from UCB to SpA CoI was not ascribed to differences in dose response or kinetics. Purified B cells from UCB were not stimulated by SpA CoI either, suggesting tht the low responsiveness was not due to the suppressive effect of T cells or macrophages, but to some intrinsic defect in B cells in UCB. These results suggest that the B cells in neonates may be more immature than the T cells.

Characterization of lymphoid cells in the blood of healthy adults: sequential immunological, cytochemical and cytokinetic studies

With a new method, sequential immunological, cytochemical and cytokinetic studies were done on lymphoid cells in the peripheral blood of 12 healthy adults. Every single lymphoid cell could therefore be characterized by the following markers: surface immunoglobulins (sIg); rosetting with sheep red blood cells (E); unspecific acid alpha-naphthyl acetate esterase (ANAE); and 3HdT incorporation. Significantly more E+sIg-ANAE-cells (51% and 22% of all lymphoid cells, respectively). Of all ANAE+ cells 90% were E+, but 64% of all ANAE- cells were also E+. In all individuals a subpopulation of E+sIg+ cells was found. The esterase pattern of these cells was similar to that of E-sIg+ cells. The overall labeling index of the lymphoid cells examined was less than or equal to 0.2%.

Cord blood lymphocyte subpopulations and mitogenic activity in whole blood microculture

Comparative studies on cord and adult blood showed that cord blood contained at least twice as many lymphocytes as adult blood. Relatively, the percentage of T cells (E-RFC) was significantly lower in cord blood lymphocytes. The percentage of B cells (EAC-RFC and SmIg bearing cells), as well as the total number of T and B cells (mm(-3)), was significantly higher in cord blood. In vitro mitogen transformation of cord and adult lymphocytes in while blood, cultured for different times and diluted to contain equivalent numbers of lymphocytes per culture, showed significant qualitative and quantitative differences. Responses to the T cell mitogens phytohaemagglutinin (PHA) and concanavalin A (Con A) were examined from 3 to 6 days in culture. Cord blood lymphocytes were significantly more responsive when cultured for 3 to 4 days, similar to adult cells after 5 days, but significantly less responsive after 6 days in culture. The optimal levels of T cell mitogen responsiveness in cord cells (Day 4) were similar to adut cells (Day 6). Spontaneous transformation of unstimulated lymphocytes and B cell mitogen transformation with pokeweed mitogen (PWM) and staphylococcal protein A (SpA) were all significantly higher in cord blood than in adult whole blood cultured for 5 days.

Age-dependent changes in the electrophoretic mobilities of human blood lymphocytes

The distribution of the anodic electrophoretic mobilities (EPM) of human peripheral blood lymphocytes was determined for lymphocytes isolated from umbilical cord blood and from blood of individuals 6 months to 93 years of age. The distribution was bimodal in infants up to 2 years of age and suggested a small percentage of cells with a mobility of 0.95 micrometer s-1 V-1 cm. this value was chosen to discriminate between low-mobility cells (LMCs) and high-mobility cells (HMCs). The relative percentage of LMCs increased from birth to 2 years and two types of LMCs could be distinguished. The distribution was unimodal and asymmetric in children and adults and nearly Gaussian in aged people. Substantial differences between the distributions of the lymphocyte EPMs were seen on comparison of the histograms for individuals of similar ages. The analysis of the distribution of the lymphocyte EPMs on cell suspensions enriched in, or depleted of T or B cells confirmed the mobility of most T cells to be higher than the mobility of most B cells, whatever the age of the individual. The distribution of lymphocyte EPMs determined in the same adult over a 6 year period showed minor variations.

Fetal blood-borne myelo- and thrombopoietic stem cells in diffusion chambers

The potential of hematopoietic stem cells from cord blood for proliferation and differentiation have been studied by the diffusion chamber technique. In a pilot study, it was shown that blast cell production and myelopoiesis from the original lymphoid cell suspension starts 6 days after implantation. Mature granulocytes and megakaryocytes respectively appear in the chambers from the 16th and 10th days onwards. Myelopoiesis is ten times more active in fetal than in adult blood. There were thrombopoietic stem cells in 7 of 10 cord blood samples but in only one of 10 adult blood specimens. It is concluded that the high hematopoietic activity of the bone marrow at term is reflected by an increase in the number of stem cells circulating in the blood. Myelo- and thrombopoietic stem cells must be sought among the lymphoid cells of the original cord blood cell suspension.

Haematopoietic stem cells (CFUc) in human cord blood

Colony forming units (CFUc) giving rise to myelocytic colonies in methylcellulose cultures were found among non-adherent mononuclear cells of human cord blood with a frequency of one in 1678. The number decreased makredly during the first 8 to 10 days of life. They were rarely detected in adult blood by this technique.

Comparison of RNA and DNA synthesis, spontaneous and PHa induced, between blood lymphoid cells of newborn infants, older infants, and adults. A study of scintillation counting and by autoradiography

Spontaneous and PHA induced RNA and DNA synthesis was measured qualitatively by autoradiography and quantitatively by scintillation counting in blood lymphoic cells of newborn infants, older infants, and adults. Spontaneous RNA synthesis was found in transitional cells, large phagocytic lymphoid cells and lymphocytes. Transitional cells and phagocytic lymphoid cells also synthesized DNA spontaneously. Quantitatively, spontaneous RNA synthesis was active in both newborn infants and in adults, but significantly less so in older infants. PHA stimulation for 18 h increased RNA synthesis significantly in blood lymphoid cells of newborn infants and adults, and to a much lesser but still significant degree in older infants. Spontaneous DNA synthesis was significantly greater in newborn infants than in older infants and adults. PHA stimulation for 18 h had no effect on thymidine incorporation in any of the groups studied.

Cytoplasmic DNA synthesis by cord blood cells of premature and full-term infants: an autoradiographic study

Cord blood cells from 8 full-term and 12 premature infants as well as blood leukocytes from 10 adults were incubated with 3H-thymidine and were subsequently exposed to autoradiographic emulsion for prolonged periods of 45 and 90 days. Cytoplasmic label -- which were interpreted as evidence of mitochondrial DNA synthesis -- was found in 1.7 per cent of lymphoid cells from adult blood, in 2.9 per cent and 4.5 per cent of lymphoid cells from full-term and premature infants, respectively. Statistical analysis of the data shows that the number of labelled cells is significantly larger in the blood of premature infants than in adults (p less than 0.01).

IgG on infants' B lymphocytes: enhanced binding of IgG by Ig M-bearing lymphoid cells in early childhood

IgM/IgD-bearing lymphocytes (B cells) from children in the first few weeks of life were found to also have surface IgG, unlike most normal adult B cells. The IgG was loosely bound to the lymphocyte surface and was partially or completely removed by incubation at 37 degrees C or by trypsinization. When F(ab')2 antisera were employed, very few infant B cells had surface IgG, although the IgM staining was similar to that obtained with the native antisera. IgM/IgD-positive cells bound IgG anti-Rh-coated (Ripley) erythrocytes, unlike most adult B lymphocytes. Capping experiments suggested that an Fc receptor on the cells could be redistributed by the anti-IgM-surface IgM complex. These data indicate that, during infancy, B-lymphocyte receptors for IgG are of altered affinity, frequency, or availability compared with adult B-lymphocyte Fc receptors and resemble the Fc receptors found on "third population" (Fc + Ig-) mononuclear cells and monocytes.

Cells in spontaneous DNA synthesis in cord blood of premature and full-term newborn infants. An autoradiographic study

Cord blood from 16 premature infants and 10 full-term infants, and blood from 10 healthy adults, was incubated for 30 minutes with tritiated thymidine, after which an autoradiographic study was made of spontaneously labeling cells. Apart from a varying number of erythroblasts, myelocytes, and an occasional blast cell, two main types of spontaneously labeling cells were observed: transitional cells and large lymphoid cells, previously shown to be phagocytic. Spontaneously labeling cells were 12 times more frequent in cord blood of premature and full-term infants than in the blood of adults. No transitional cells were seen in adult blood.