Virus dissemination via the lymphomyeloid complex.

In the previous AIDS symposium organized by the Society, Witte and Witte (1) made a number of predictions, one of which was that in AIDS patients, "Lymph from the thoracic duct should be strongly positive for HIV." Though direct evidence for this is lacking, some early experiments of ours with vaccinia virus (2) are fully in accord with this prediction, to which they lend indirect support. In rabbits, nasally instilled vaccinia virus spreads via the lymphatic pathway (afferent peripheral lymph--deep cervical gland--efferent lymph--thoracic duct) in as short a time as nine hours.

Stem cell kinetics: correlation of in vivo and in vitro data.

Comparisons have been made along three parameters between the observations of a number of workers regarding in vivo the transitional cell compartment, and in vitro observations of colony-forming units. The parameters used were size changes when the stem cell requirements are increased, the existence of three size groups in both the transitional cell compartment and in the colony-forming units examined, and the relation between cell size and the percentage of cells in DNA synthesis. On all these parameters there appears to be close correlation between the in vitro properties of stem cells and progenitor cells and the in vivo properties of the transitional cell compartment.

DNA synthesis in peritoneal lymphoid cells. Indirect induction of changes.

Changes were observed in the DNA-synthesising cells of the murine peritoneal cavity after a single subcutaneous injection of (1) fluid thioglycollate medium, (2) guinea-pig serum, (3) pertussis vaccine, (4) fresh egg albumen, (5) bovine albumin Fraction 5, (6) normal saline as control. The subcutaneous route was chosen in order to avoid direct peritoneal irritation. A total of 180 animals was employed, in six groups of 30 each, and in each group five animals per day were examined for six days.

Phagocytic lymphoid cells and transitional cells in the peritoneal cavity.

In 71 mice, a study was made of the non-granular phagocytic cells in the peritoneal cavity, both after the intraperitoneal injection of India ink, and by incubation of the non-adherent cells with ink in vitro. Ink was taken up by a number of lymphoid cells, as well as by macrophages and monocytes, referred to jointly as macrophages. In addition, the presence of DNA-synthesizing cells was investigated by radio-autography after incubation of cell suspensions for 1 hour with tritiated thymidine.

Studies on transitional cells. I. Kinetic changes in rat bone marrow during hypoxia and rebound.

Kinetic changes have been studied in the transitional cells of the marrow in normal, hypoxic (0.5 atm) and rebound rats. Suspensions of marrow cells were incubated with tritiated thymidine for 1 hour, and the percentage of labelled transitionals of all sizes, as well as of large transitionals, was couinted in radioautographs.

The lymphocyte production pathway in bone marrow: possible significance of the size spectrum of lymphocytes and their precursors.

It is now generally accepted that transitional ('lymphoid') cells are the precursors of small lymphocytes. Such cells have a heterogeneous size spectrum and show high proliferative capacity. To facilitate the study of the kinetics of lymphocyte production, a detailed investigation of cell sizes of the transitional cell-lymphocyte compartment was carried out using a Coulter counter modified to permit a very rapid and accurate examination of cells in suspension.

Successive stimulation of major cell groups in bone marrow. A preliminary approach to the problem of stem cell competition.

The existence of pluripotential haemopoietic stem cells raises the possibility of stem cell competition when two or more differentiating stimuli are given either simultaneously or in close succession. The experiments now reported deal with the effects on guinea pig bone marrow of successive stimulation and they fall into two groups. In one group, erythropoiesis was first stimulated by means of hypoxia, after which granulopoiesis was stimulated by the intraperitoneal injection of typhoid vaccine.

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.

Establishment in continuous culture of a new type of lymphocyte from a "Burkitt like" malignant lymphoma (line D.G.-75).

The isolation and establishment in vitro of a hitherto undescribed type of lymphocyte designated D.G.-75 is reported.

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.

Histogenesis of B and T lymphocytes.

There are striking differences in the histogenesis of B and T cells. 1) The formation of B lymphocytes seems to be closely associated with that of other blood cells, whereas the formation of T cells is not. 2) In postnatal life, the bone marrow is a mojor site for the formation of B cells, while T cells are produced mainly in the thymus.